diff --git a/exercises/00_hello_world/main.cpp b/exercises/00_hello_world/main.cpp
index 8866f3c15..2f5982d1b 100644
--- a/exercises/00_hello_world/main.cpp
+++ b/exercises/00_hello_world/main.cpp
@@ -1,11 +1,12 @@
 #include "../exercise.h"
-
+using namespace std;
 // READ: std streams <https://zh.cppreference.com/w/cpp/io/c/std_streams>
 // READ: 流修饰符 <https://zh.cppreference.com/w/cpp/io/manip>
 // READ: format in cxx20 <https://zh.cppreference.com/w/cpp/utility/format/format>
 
 int main(int argc, char **argv) {
     // TODO: 在控制台输出 "Hello, InfiniTensor!" 并换行
-    std::cout : "Hello, InfiniTensor!" + std::endl;
+    // std::cout : "Hello, InfiniTensor!" + std::endl;
+    std::cout<<"Hello, InfiniTensor!"<<endl;
     return 0;
 }
diff --git a/exercises/01_variable&add/main.cpp b/exercises/01_variable&add/main.cpp
index 5014863fd..ccae6eb93 100644
--- a/exercises/01_variable&add/main.cpp
+++ b/exercises/01_variable&add/main.cpp
@@ -5,6 +5,7 @@
 int main(int argc, char **argv) {
     // TODO: 补全变量定义并打印加法运算
     // x ?
+    int x=5;
     std::cout << x << " + " << x << " = " << x + x << std::endl;
     return 0;
 }
diff --git a/exercises/02_function/main.cpp b/exercises/02_function/main.cpp
index b5eef7f28..44c4180f2 100644
--- a/exercises/02_function/main.cpp
+++ b/exercises/02_function/main.cpp
@@ -6,6 +6,8 @@
 
 // TODO: 在这里声明函数
 
+int add(int a, int b);
+
 int main(int argc, char **argv) {
     ASSERT(add(123, 456) == 123 + 456, "add(123, 456) should be 123 + 456");
 
@@ -16,4 +18,5 @@ int main(int argc, char **argv) {
 
 int add(int a, int b) {
     // TODO: 补全函数定义，但不要移动代码行
+    return a + b;
 }
diff --git a/exercises/03_argument&parameter/main.cpp b/exercises/03_argument&parameter/main.cpp
index 7fb5d3c2f..0ff2e2d54 100644
--- a/exercises/03_argument&parameter/main.cpp
+++ b/exercises/03_argument&parameter/main.cpp
@@ -8,19 +8,19 @@ void func(int);
 // TODO: 为下列 ASSERT 填写正确的值
 int main(int argc, char **argv) {
     auto arg = 99;
-    ASSERT(arg == ?, "arg should be ?");
+    ASSERT(arg == 99, "arg should be 99");
     std::cout << "befor func call: " << arg << std::endl;
     func(arg);
-    ASSERT(arg == ?, "arg should be ?");
+    ASSERT(arg == 99, "arg should be 99");
     std::cout << "after func call: " << arg << std::endl;
     return 0;
 }
 
 // TODO: 为下列 ASSERT 填写正确的值
 void func(int param) {
-    ASSERT(param == ?, "param should be ?");
+    ASSERT(param == 99, "param should be 99");
     std::cout << "befor add: " << param << std::endl;
     param += 1;
-    ASSERT(param == ?, "param should be ?");
+    ASSERT(param == 100, "param should be 100");
     std::cout << "after add: " << param << std::endl;
 }
diff --git a/exercises/04_static/main.cpp b/exercises/04_static/main.cpp
index f107762fa..e1cf3af87 100644
--- a/exercises/04_static/main.cpp
+++ b/exercises/04_static/main.cpp
@@ -2,6 +2,12 @@
 
 // READ: `static` 关键字 <https://zh.cppreference.com/w/cpp/language/storage_duration>
 // THINK: 这个函数的两个 `static` 各自的作用是什么？
+
+// static修饰func函数，表示这个函数只在这个.cpp文件中可见
+// 其作用是防止重复定义,如果在另一个.cpp文件中定义了这个函数，加上static后，这两个函数就不会冲突，编译器不会发生“重复定义”错误
+
+// static修饰static_局部变量，其作用是`静态存储期`
+// 该变量**只初始化一次**，函数在运行结束后，变量不会被销毁，而是保存在内存中
 static int func(int param) {
     static int static_ = param;
     // std::cout << "static_ = " << static_ << std::endl;
@@ -10,10 +16,10 @@ static int func(int param) {
 
 int main(int argc, char **argv) {
     // TODO: 将下列 `?` 替换为正确的数字
-    ASSERT(func(5) == ?, "static variable value incorrect");
-    ASSERT(func(4) == ?, "static variable value incorrect");
-    ASSERT(func(3) == ?, "static variable value incorrect");
-    ASSERT(func(2) == ?, "static variable value incorrect");
-    ASSERT(func(1) == ?, "static variable value incorrect");
+    ASSERT(func(5) == 5, "static variable value incorrect");
+    ASSERT(func(4) == 6, "static variable value incorrect");
+    ASSERT(func(3) == 7, "static variable value incorrect");
+    ASSERT(func(2) == 8, "static variable value incorrect");
+    ASSERT(func(1) == 9, "static variable value incorrect");
     return 0;
 }
diff --git a/exercises/05_constexpr/main.cpp b/exercises/05_constexpr/main.cpp
index d1db6c9d8..8755175ef 100644
--- a/exercises/05_constexpr/main.cpp
+++ b/exercises/05_constexpr/main.cpp
@@ -1,5 +1,7 @@
 #include "../exercise.h"
 
+// constexpr（constant expression），常量表达式
+// 告诉编译器，这是一个常量，需要在编译期间就要进行计算
 constexpr unsigned long long fibonacci(int i) {
     switch (i) {
         case 0:
@@ -19,8 +21,7 @@ int main(int argc, char **argv) {
     // TODO: 观察错误信息，修改一处，使代码编译运行
     // PS: 编译运行，但是不一定能算出结果……
     constexpr auto ANS_N = 90;
-    constexpr auto ANS = fibonacci(ANS_N);
+    auto ANS = fibonacci(ANS_N);
     std::cout << "fibonacci(" << ANS_N << ") = " << ANS << std::endl;
-
     return 0;
 }
diff --git a/exercises/06_array/main.cpp b/exercises/06_array/main.cpp
index 61ed99ec0..e853e29f8 100644
--- a/exercises/06_array/main.cpp
+++ b/exercises/06_array/main.cpp
@@ -2,6 +2,7 @@
 
 // READ: 数组 <https://zh.cppreference.com/w/cpp/language/array>
 
+// 数组定义
 unsigned long long arr[90]{0, 1};
 unsigned long long fibonacci(int i) {
     switch (i) {
@@ -11,13 +12,15 @@ unsigned long long fibonacci(int i) {
             return 1;
         default:
             // TODO: 补全三目表达式缺失的部分
-            return <condition> ? <cache> : (arr[i] = fibonacci(i - 1) + fibonacci(i - 2));
+            return arr[i]!=0 ? arr[i] : (arr[i] = fibonacci(i - 1) + fibonacci(i - 2));
     }
 }
 
 int main(int argc, char **argv) {
     // TODO: 为此 ASSERT 填写正确的值
-    ASSERT(sizeof(arr) == ?, "sizeof array is size of all its elements");
+    // std::cout<<sizeof(arr)<<std::endl;
+    // unsigned long long 为 8 个字节
+    ASSERT(sizeof(arr) == 720, "sizeof array is size of all its elements");
     // ---- 不要修改以下代码 ----
     ASSERT(fibonacci(2) == 1, "fibonacci(2) should be 1");
     ASSERT(fibonacci(20) == 6765, "fibonacci(20) should be 6765");
diff --git a/exercises/07_loop/main.cpp b/exercises/07_loop/main.cpp
index 44fd835cd..cc7e43087 100644
--- a/exercises/07_loop/main.cpp
+++ b/exercises/07_loop/main.cpp
@@ -5,9 +5,9 @@
 // READ: 纯函数 <https://zh.wikipedia.org/wiki/%E7%BA%AF%E5%87%BD%E6%95%B0>
 static unsigned long long fibonacci(int i) {
     // TODO: 为缓存设置正确的初始值
-    static unsigned long long cache[96], cached;
+    static unsigned long long cache[96]{0,1}, cached=2;
     // TODO: 设置正确的循环条件
-    for (; false; ++cached) {
+    for (; cached<96; ++cached) {
         cache[cached] = cache[cached - 1] + cache[cached - 2];
     }
     return cache[i];
diff --git a/exercises/08_pointer/main.cpp b/exercises/08_pointer/main.cpp
index ba37173f5..754d2d816 100644
--- a/exercises/08_pointer/main.cpp
+++ b/exercises/08_pointer/main.cpp
@@ -1,10 +1,20 @@
 #include "../exercise.h"
 
 // READ: 数组向指针退化 <https://zh.cppreference.com/w/cpp/language/array#%E6%95%B0%E7%BB%84%E5%88%B0%E6%8C%87%E9%92%88%E7%9A%84%E9%80%80%E5%8C%96>
+//bool is_fibonacci(int ptr[], int len, int stride)
 bool is_fibonacci(int *ptr, int len, int stride) {
     ASSERT(len >= 3, "`len` should be at least 3");
     // TODO: 编写代码判断从 ptr 开始，每 stride 个元素取 1 个元素，组成长度为 n 的数列是否满足
     // arr[i + 2] = arr[i] + arr[i + 1]
+    for(int i = 0;i<len-2;++i){
+        //int current=ptr[i*stride];
+        int current = *(ptr+i*stride);
+        int next = *(ptr+(i+1)*stride);
+        int next_next = *(ptr+(i+2)*stride);
+        if(current+next!=next_next){
+            return false;
+        }
+    }
     return true;
 }
 
diff --git a/exercises/09_enum&union/main.cpp b/exercises/09_enum&union/main.cpp
index 3f2cec768..4973fc938 100644
--- a/exercises/09_enum&union/main.cpp
+++ b/exercises/09_enum&union/main.cpp
@@ -2,10 +2,15 @@
 
 // READ: 枚举类型 <https://zh.cppreference.com/w/cpp/language/enum>
 
+// enum（枚举）是一种用户自定义的数据类型，用于为一组`整数常量`分配好听的名字。使用枚举可以让代码更具可读性和可维护性。
+
 // `enum` 是 C 的兼容类型，本质上其对应类型的常量。
 // 在 `enum` 中定义标识符等价于定义 constexpr 常量，
 // 这些标识符不需要前缀，可以直接引用。
 // 因此 `enum` 定义会污染命名空间。
+
+// 不限定作用域枚举，不推荐作法
+// 可以实现隐式转换：int x =Red
 enum ColorEnum : unsigned char {
     COLOR_RED = 31,
     COLOR_GREEN,
@@ -16,6 +21,10 @@ enum ColorEnum : unsigned char {
 // 有作用域枚举型是 C++ 引入的类型安全枚举。
 // 其内部标识符需要带前缀引用，如 `Color::Red`。
 // 作用域枚举型可以避免命名空间污染，并提供类型安全保证。
+
+// 限定作用域枚举，推荐做法
+// 使用时必须带上类名（作用域）
+// TrafficLight s = TrafficLight::RED;
 enum class Color : int {
     Red = COLOR_RED,
     Green,
@@ -30,6 +39,9 @@ ColorEnum convert_by_pun(Color c) {
     // 但这种写法实际上仅在 C 语言良定义，在 C++ 中是未定义行为。
     // 这是比较少见的 C++ 不与 C 保持兼容的特性。
     // READ: 类型双关 <https://tttapa.github.io/Pages/Programming/Cpp/Practices/type-punning.html>
+
+    //union（联合体/共用体）是 C++ 中一种特殊的类类型。它最显著的特征是：所有成员共享同一块内存地址
+    //但在同一时刻只能使用其中的一个成员，这就意味着数据会被覆盖，是一种极端节省内存的写法
     union TypePun {
         ColorEnum e;
         Color c;
@@ -37,7 +49,7 @@ ColorEnum convert_by_pun(Color c) {
 
     TypePun pun;
     // TODO: 补全类型双关转换
-
+    pun.c = c;//c值写入，e值被覆盖
     return pun.e;
 }
 
diff --git a/exercises/10_trivial/main.cpp b/exercises/10_trivial/main.cpp
index 6ba23e48e..fdbc6f163 100644
--- a/exercises/10_trivial/main.cpp
+++ b/exercises/10_trivial/main.cpp
@@ -8,18 +8,27 @@ struct FibonacciCache {
 };
 
 // TODO: 实现正确的缓存优化斐波那契计算
-static unsigned long long fibonacci(FibonacciCache &cache, int i) {
-    for (; false; ++cached) {
-        cache[cached] = cache[cached - 1] + cache[cached - 2];
+// static unsigned long long fibonacci(FibonacciCache &cache, int i) {
+//     for (; false; ++cached) {
+//         cache[cached] = cache[cached - 1] + cache[cached - 2];
+//     }
+//     return cache.cache[i];
+// }
+static unsigned long long fibonacci(FibonacciCache &cache, int i){
+    if(i>=16){
+        return 0;
+    }
+    for(;cache.cached<=i;++cache.cached){
+        cache.cache[cache.cached]=cache.cache[cache.cached-1]+cache.cache[cache.cached-2];
     }
     return cache.cache[i];
-}
 
+}
 int main(int argc, char **argv) {
     // TODO: 初始化缓存结构体，使计算正确
     // NOTICE: C/C++ 中，读取未初始化的变量（包括结构体变量）是未定义行为
     // READ: 初始化的各种写法 <https://zh.cppreference.com/w/cpp/language/initialization>
-    FibonacciCache fib;
+    FibonacciCache fib{{0,1},2};
     ASSERT(fibonacci(fib, 10) == 55, "fibonacci(10) should be 55");
     std::cout << "fibonacci(10) = " << fibonacci(fib, 10) << std::endl;
     return 0;
diff --git a/exercises/11_method/main.cpp b/exercises/11_method/main.cpp
index 0e08e0a36..8686d89fa 100644
--- a/exercises/11_method/main.cpp
+++ b/exercises/11_method/main.cpp
@@ -6,16 +6,19 @@ struct Fibonacci {
 
     // TODO: 实现正确的缓存优化斐波那契计算
     unsigned long long get(int i) {
-        for (; false; ++cached) {
-            cache[cached] = cache[cached - 1] + cache[cached - 2];
+        if (i>=128){
+            return 0;
         }
-        return cache[i];
+        for (; this->cached<=i; ++this->cached) {
+            this->cache[this->cached] = this->cache[this->cached - 1] + this->cache[this->cached - 2];
+        }
+        return this->cache[i];
     }
 };
 
 int main(int argc, char **argv) {
     // TODO: 初始化缓存结构体，使计算正确
-    Fibonacci fib;
+    Fibonacci fib{{0,1},2};
     ASSERT(fib.get(10) == 55, "fibonacci(10) should be 55");
     std::cout << "fibonacci(10) = " << fib.get(10) << std::endl;
     return 0;
diff --git a/exercises/12_method_const/main.cpp b/exercises/12_method_const/main.cpp
index 5521be4da..a0cea179e 100644
--- a/exercises/12_method_const/main.cpp
+++ b/exercises/12_method_const/main.cpp
@@ -5,11 +5,20 @@
 struct Fibonacci {
     int numbers[11];
     // TODO: 修改方法签名和实现，使测试通过
-    int get(int i) {
+    // int get(int i) {
+    // }
+    int get(int i) const {
+        if (i<0 || i>=11)
+        {
+            return 0;
+        }
+        
+        return numbers[i];
     }
 };
 
 int main(int argc, char **argv) {
+    //关键字 constexpr 意味着对象 FIB 是编译期常量，它隐含了 const 属性。在 C++ 中，const 对象只能调用 const 成员函数。
     Fibonacci constexpr FIB{{0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55}};
     ASSERT(FIB.get(10) == 55, "fibonacci(10) should be 55");
     std::cout << "fibonacci(10) = " << FIB.get(10) << std::endl;
diff --git a/exercises/13_class/main.cpp b/exercises/13_class/main.cpp
index 9afa98c5b..fca2cbcb7 100644
--- a/exercises/13_class/main.cpp
+++ b/exercises/13_class/main.cpp
@@ -9,17 +9,23 @@
 // 因此必须提供构造器来初始化字段。
 // READ: 构造器 <https://zh.cppreference.com/w/cpp/language/constructor>
 class Fibonacci {
+    //size_t 无符号整数类型
     size_t cache[16];
     int cached;
 
 public:
     // TODO: 实现构造器
     // Fibonacci()
+    Fibonacci(){
+       this->cache[0]=0;
+       this->cache[1]=1;
+       this->cached=2; 
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
-            cache[cached] = cache[cached - 1] + cache[cached - 2];
+        for (; this->cached <= i; ++this->cached) {
+            this->cache[this->cached] = this->cache[this->cached - 1] + this->cache[this->cached - 2];
         }
         return cache[i];
     }
diff --git a/exercises/14_class_destruct/main.cpp b/exercises/14_class_destruct/main.cpp
index 42150e8ca..846c45b9b 100644
--- a/exercises/14_class_destruct/main.cpp
+++ b/exercises/14_class_destruct/main.cpp
@@ -11,15 +11,24 @@ class DynFibonacci {
 
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    // cache = new size_t[capacity];动态初始化数组
+    // 成员初始化列表（Member Initializer List）：构造函数：函数名(参数) : 成员1(初始化), 成员2(初始化) { 函数体 }
+    DynFibonacci(int capacity): cache(new size_t[capacity]), cached(2) {
+        cache[0] = 0;
+        cache[1] = 1;
+    }
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci() {
+        // 使用 delete[]：因为 cache 是用 new[] 分配的数组
+        // 如果用 delete cache（没有 []），会导致未定义行为
+        delete[] cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
-            cache[cached] = cache[cached - 1] + cache[cached - 2];
+        for (; this->cached <= i; ++this->cached) {
+            this->cache[this->cached] = this->cache[this->cached - 1] + this->cache[this->cached - 2];
         }
         return cache[i];
     }
diff --git a/exercises/15_class_clone/main.cpp b/exercises/15_class_clone/main.cpp
index f74b70391..17dd8b344 100644
--- a/exercises/15_class_clone/main.cpp
+++ b/exercises/15_class_clone/main.cpp
@@ -7,21 +7,32 @@
 class DynFibonacci {
     size_t *cache;
     int cached;
-
+    int capacity;//记录容量
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    // DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    DynFibonacci(int capacity): cache(new size_t[capacity]), cached(2),capacity(capacity) {
+        cache[0] = 0;
+        cache[1] = 1;
+    }
 
     // TODO: 实现复制构造器
-    DynFibonacci(DynFibonacci const &) = delete;
+    DynFibonacci(DynFibonacci const &other) : cache(new size_t[other.capacity]), cached(other.cached), capacity(other.capacity) {
+        //复制 cache
+        for (int i = 0; i < other.cached; ++i) {
+            this->cache[i] = other.cache[i];
+        }
+    };
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci(){
+        delete[] cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
-            cache[cached] = cache[cached - 1] + cache[cached - 2];
+        for (; this->cached <= i; ++this->cached) {
+            this->cache[this->cached] = this->cache[this->cached - 1] + this->cache[this->cached - 2];
         }
         return cache[i];
     }
diff --git a/exercises/16_class_move/main.cpp b/exercises/16_class_move/main.cpp
index 8d2c421da..50920f54c 100644
--- a/exercises/16_class_move/main.cpp
+++ b/exercises/16_class_move/main.cpp
@@ -9,27 +9,62 @@
 // READ: 移动赋值 <https://zh.cppreference.com/w/cpp/language/move_assignment>
 // READ: 运算符重载 <https://zh.cppreference.com/w/cpp/language/operators>
 
+// 左值 (Lvalue) vs 右值 (Rvalue):
+//    - 左值：有名字、有固定地址的对象（如变量名 fib）。可以取址&。
+//    - 右值：临时的、即将销毁的对象（如 std::move(fib) 的返回值，或临时计算结果）。不能取址&。
+//    - 右值引用（Rvalue Reference） 是 C++11 引入的一种新引用类型，专门用来绑定到临时对象（右值）上。
+// 移动语义 (Move Semantics):
+//    - 核心在于“接管”资源而非“复制”资源。对于动态分配的内存，移动只需交换指针。
+//    - 核心思想：“剪切 + 粘贴” 而不是 “复制 + 粘贴”。
+// 换言之，移动语义意味着“接管”资源而非“复制”资源。
+// noexcept:
+//    - 移动构造和移动赋值通常标记为 noexcept，告知编译器此操作不会抛出异常，
+//      这对于 std::vector 等容器在扩容时的性能优化至关重要。
 class DynFibonacci {
     size_t *cache;
     int cached;
 
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    DynFibonacci(int capacity): cache(new size_t[capacity]), cached(2) {
+        if (capacity>0) cache[0] = 0;
+        if (capacity>1) cache[1] = 1;
+    }
 
     // TODO: 实现移动构造器
-    DynFibonacci(DynFibonacci &&) noexcept = delete;
+    // 通过右值引用(&&),接管 other 的资源，将other置于有效但未定义状态(指针置空)
+    DynFibonacci(DynFibonacci && other) noexcept : cache(other.cache), cached(other.cached) {
+        // 断开对原对象的内存引用
+        other.cache = nullptr;
+        other.cached = 0;
+    }
 
     // TODO: 实现移动赋值
     // NOTICE: ⚠ 注意移动到自身问题 ⚠
-    DynFibonacci &operator=(DynFibonacci &&) noexcept = delete;
+    // 移动赋值需要先释放自己的资源，再接管别人的资源
+    DynFibonacci &operator=(DynFibonacci &&other) noexcept {
+        //自赋值检查，防止fib=std::move(fib)导致资源提取释放
+        if(this!= &other){
+            //1.释放旧资源
+            delete[] cache;
+            //2.接管新资源
+            cache = other.cache;
+            cached = other.cached;
+            //3.断开对原对象的内存引用
+            other.cache = nullptr;
+            other.cached = 0;
+        }
+        return *this;
+    }
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci(){
+        delete[] cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t operator[](int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
diff --git a/exercises/17_class_derive/main.cpp b/exercises/17_class_derive/main.cpp
index 819ae72fc..3cd299646 100644
--- a/exercises/17_class_derive/main.cpp
+++ b/exercises/17_class_derive/main.cpp
@@ -30,9 +30,12 @@ struct A {
         std::cout << ++i << ". " << "~A(" << a << ')' << std::endl;
     }
 };
+// `:public`：表示继承public和protected对象，权限不变
+// `:private`：表示继承public和protected对象，权限变为private
+// `:protected`：表示继承public和protected对象，权限变为protected
 struct B : public A {
     X x;
-
+    
     B(int b) : A(1), x(b) {
         std::cout << ++i << ". " << "B(" << a << ", X(" << x.x << "))" << std::endl;
     }
@@ -50,9 +53,9 @@ int main(int argc, char **argv) {
     B b = B(3);
 
     // TODO: 补全三个类型的大小
-    static_assert(sizeof(X) == ?, "There is an int in X");
-    static_assert(sizeof(A) == ?, "There is an int in A");
-    static_assert(sizeof(B) == ?, "B is an A with an X");
+    static_assert(sizeof(X) == 4, "There is an int in X");
+    static_assert(sizeof(A) == 4, "There is an int in A");
+    static_assert(sizeof(B) == 8, "B is an A with an X");
 
     i = 0;
     std::cout << std::endl
diff --git a/exercises/18_class_virtual/main.cpp b/exercises/18_class_virtual/main.cpp
index ac6382413..8603652cf 100644
--- a/exercises/18_class_virtual/main.cpp
+++ b/exercises/18_class_virtual/main.cpp
@@ -1,7 +1,34 @@
 #include "../exercise.h"
 
 // READ: 虚函数 <https://zh.cppreference.com/w/cpp/language/virtual>
+// 虚函数（Virtual Function） 是实现多态（Polymorphism）的核心机制。
+// - 它允许你在派生类（子类）中重写基类（父类）定义的函数
+// - 并确保通过基类指针或引用调用该函数时，实际执行的是子类中的版本。
+// <---->
+// 虚函数：
+// - 在基类中使用关键字 virtual 声明的函数称为虚函数。
+// - 在派生类使用override 关键字用于明确表示重写
+// class Base {
+// public:
+//     virtual void show() {
+//         cout << "这是基类的 show 函数" << endl;
+//     }
+// };
+// class Derived : public Base {
+// public:
+//     void show() override { // override 关键字用于明确表示重写（C++11）
+//         cout << "这是派生类的 show 函数" << endl;
+//     }
+// };
+// <---->
+// final 关键字有两个主要用途：禁止虚函数被进一步重写 以及 禁止类被继承。
+// - 当在派生类中将一个虚函数标记为 final 时，任何尝试在更深层的子类中重写该函数的行为都会导致编译错误。
+// - 如果将 final 放在类名后面，则表示该类是“最终类”，不允许任何类继承它。
 
+// 核心口诀：
+// - 虚函数看对象（实际是谁就调谁）。
+// - 普通函数看类型（声明是谁就调谁）。
+// - final 锁死子类（不影响父类引用调自己）。
 struct A {
     virtual char virtual_name() const {
         return 'A';
@@ -42,38 +69,38 @@ int main(int argc, char **argv) {
     C c;
     D d;
 
-    ASSERT(a.virtual_name() == '?', MSG);
-    ASSERT(b.virtual_name() == '?', MSG);
-    ASSERT(c.virtual_name() == '?', MSG);
-    ASSERT(d.virtual_name() == '?', MSG);
-    ASSERT(a.direct_name() == '?', MSG);
-    ASSERT(b.direct_name() == '?', MSG);
-    ASSERT(c.direct_name() == '?', MSG);
-    ASSERT(d.direct_name() == '?', MSG);
+    ASSERT(a.virtual_name() == 'A', MSG);
+    ASSERT(b.virtual_name() == 'B', MSG);
+    ASSERT(c.virtual_name() == 'C', MSG);
+    ASSERT(d.virtual_name() == 'C', MSG);
+    ASSERT(a.direct_name() == 'A', MSG);
+    ASSERT(b.direct_name() == 'B', MSG);
+    ASSERT(c.direct_name() == 'C', MSG);
+    ASSERT(d.direct_name() == 'D', MSG);
 
     A &rab = b;
     B &rbc = c;
     C &rcd = d;
 
-    ASSERT(rab.virtual_name() == '?', MSG);
-    ASSERT(rbc.virtual_name() == '?', MSG);
-    ASSERT(rcd.virtual_name() == '?', MSG);
-    ASSERT(rab.direct_name() == '?', MSG);
-    ASSERT(rbc.direct_name() == '?', MSG);
-    ASSERT(rcd.direct_name() == '?', MSG);
+    ASSERT(rab.virtual_name() == 'B', MSG);
+    ASSERT(rbc.virtual_name() == 'C', MSG);
+    ASSERT(rcd.virtual_name() == 'C', MSG);
+    ASSERT(rab.direct_name() == 'A', MSG);
+    ASSERT(rbc.direct_name() == 'B', MSG);
+    ASSERT(rcd.direct_name() == 'C', MSG);
 
     A &rac = c;
     B &rbd = d;
 
-    ASSERT(rac.virtual_name() == '?', MSG);
-    ASSERT(rbd.virtual_name() == '?', MSG);
-    ASSERT(rac.direct_name() == '?', MSG);
-    ASSERT(rbd.direct_name() == '?', MSG);
+    ASSERT(rac.virtual_name() == 'C', MSG);
+    ASSERT(rbd.virtual_name() == 'C', MSG);
+    ASSERT(rac.direct_name() == 'A', MSG);
+    ASSERT(rbd.direct_name() == 'B', MSG);
 
     A &rad = d;
 
-    ASSERT(rad.virtual_name() == '?', MSG);
-    ASSERT(rad.direct_name() == '?', MSG);
+    ASSERT(rad.virtual_name() == 'C', MSG);
+    ASSERT(rad.direct_name() == 'A', MSG);
 
     return 0;
 }
diff --git a/exercises/19_class_virtual_destruct/main.cpp b/exercises/19_class_virtual_destruct/main.cpp
index cdd54f74f..c21a0e05d 100644
--- a/exercises/19_class_virtual_destruct/main.cpp
+++ b/exercises/19_class_virtual_destruct/main.cpp
@@ -5,12 +5,15 @@
 
 struct A {
     // TODO: 正确初始化静态字段
-    static int num_a = 0;
+    // 使用 inline static 在类内完成初始化
+    // C++17 及以上版本支持 inline static 字段初始化
+    inline static int num_a = 0;
 
     A() {
         ++num_a;
     }
-    ~A() {
+    ///虚析构函数，确保通过基类指针删除派生类对象时，派生类的析构函数也会被调用
+    virtual ~A() {
         --num_a;
     }
 
@@ -20,13 +23,14 @@ struct A {
 };
 struct B final : public A {
     // TODO: 正确初始化静态字段
-    static int num_b = 0;
+    inline static int num_b = 0;
 
     B() {
         ++num_b;
     }
     ~B() {
         --num_b;
+
     }
 
     char name() const final {
@@ -37,10 +41,11 @@ struct B final : public A {
 int main(int argc, char **argv) {
     auto a = new A;
     auto b = new B;
-    ASSERT(A::num_a == ?, "Fill in the correct value for A::num_a");
-    ASSERT(B::num_b == ?, "Fill in the correct value for B::num_b");
-    ASSERT(a->name() == '?', "Fill in the correct value for a->name()");
-    ASSERT(b->name() == '?', "Fill in the correct value for b->name()");
+    // B 继承自 A，因此创建 B 对象时也会调用 A 的构造函数
+    ASSERT(A::num_a == 2, "Fill in the correct value for A::num_a");
+    ASSERT(B::num_b == 1, "Fill in the correct value for B::num_b");
+    ASSERT(a->name() == 'A', "Fill in the correct value for a->name()");
+    ASSERT(b->name() == 'B', "Fill in the correct value for b->name()");
 
     delete a;
     delete b;
@@ -48,13 +53,16 @@ int main(int argc, char **argv) {
     ASSERT(B::num_b == 0, "Every B was destroyed");
 
     A *ab = new B;// 派生类指针可以随意转换为基类指针
-    ASSERT(A::num_a == ?, "Fill in the correct value for A::num_a");
-    ASSERT(B::num_b == ?, "Fill in the correct value for B::num_b");
-    ASSERT(ab->name() == '?', "Fill in the correct value for ab->name()");
+    ASSERT(A::num_a == 1, "Fill in the correct value for A::num_a");
+    ASSERT(B::num_b == 1, "Fill in the correct value for B::num_b");
+    ASSERT(ab->name() == 'B', "Fill in the correct value for ab->name()");
 
     // TODO: 基类指针无法随意转换为派生类指针，补全正确的转换语句
-    B &bb = *ab;
-    ASSERT(bb.name() == '?', "Fill in the correct value for bb->name()");
+    // 1. 使用 dynamic_cast 进行安全的向下转换(推荐使用)（前提是基类有虚函数）
+    // 2. 使用 static_cast 进行不安全的向下转换（速度快，但不安全）（
+    // B &bb = *ab;
+    B &bb = dynamic_cast<B&>(*ab);
+    ASSERT(bb.name() == 'B', "Fill in the correct value for bb->name()");
 
     // TODO: ---- 以下代码不要修改，通过改正类定义解决编译问题 ----
     delete ab;// 通过指针可以删除指向的对象，即使是多态对象
diff --git a/exercises/20_function_template/main.cpp b/exercises/20_function_template/main.cpp
index cb6d978d3..31daed851 100644
--- a/exercises/20_function_template/main.cpp
+++ b/exercises/20_function_template/main.cpp
@@ -1,8 +1,16 @@
 #include "../exercise.h"
 
 // READ: 函数模板 <https://zh.cppreference.com/w/cpp/language/function_template>
+// 函数模板--`template<typename T>`,
+// - 函数模板就像是一个“模具”或“蓝图”。
+// - 不需要为 int、float 或 double 分别编写逻辑相同的函数
+// - // T1 和 T2 可以是不同类型`template <typename T1, typename T2>`
 // TODO: 将这个函数模板化
-int plus(int a, int b) {
+// int plus(int a, int b) {
+//     return a + b;
+// }
+template<typename T>
+T plus(T a, T b) {
     return a + b;
 }
 
@@ -14,7 +22,8 @@ int main(int argc, char **argv) {
     ASSERT(plus(1.25f, 2.5f) == 3.75f, "Plus two float");
     ASSERT(plus(1.25, 2.5) == 3.75, "Plus two double");
     // TODO: 修改判断条件使测试通过
-    ASSERT(plus(0.1, 0.2) == 0.3, "How to make this pass?");
+    // 浮点数精度问题，不能直接用 == 判断
+    ASSERT(std::abs(plus(0.1, 0.2) - 0.3) < 1e-9, "How to make this pass?");
 
     return 0;
 }
diff --git a/exercises/21_runtime_datatype/main.cpp b/exercises/21_runtime_datatype/main.cpp
index 9c4bf376a..3339a2dc4 100644
--- a/exercises/21_runtime_datatype/main.cpp
+++ b/exercises/21_runtime_datatype/main.cpp
@@ -18,13 +18,27 @@ struct TaggedUnion {
 };
 
 // TODO: 将这个函数模板化用于 sigmoid_dyn
-float sigmoid(float x) {
+// float sigmoid(float x) {
+//     return 1 / (1 + std::exp(-x));
+// }
+template<typename T>
+T sigmoid(T x){
     return 1 / (1 + std::exp(-x));
 }
 
 TaggedUnion sigmoid_dyn(TaggedUnion x) {
     TaggedUnion ans{x.type};
     // TODO: 根据 type 调用 sigmoid
+    // 让函数能同时处理 float 和 double
+    switch (x.type)
+    {
+    case DataType::Float:
+        ans.f = sigmoid(x.f);
+        break;
+    case DataType::Double:
+        ans.d = sigmoid(x.d);
+        break;
+    }
     return ans;
 }
 
diff --git a/exercises/22_class_template/main.cpp b/exercises/22_class_template/main.cpp
index d4985d904..1d2f1b003 100644
--- a/exercises/22_class_template/main.cpp
+++ b/exercises/22_class_template/main.cpp
@@ -1,7 +1,7 @@
 #include "../exercise.h"
 #include <cstring>
 // READ: 类模板 <https://zh.cppreference.com/w/cpp/language/class_template>
-
+// 类模板（Class Template） 是泛型编程的核心工具。它允许我们编写一个通用的类，而不必为每种数据类型都重写一遍代码。
 template<class T>
 struct Tensor4D {
     unsigned int shape[4];
@@ -10,6 +10,10 @@ struct Tensor4D {
     Tensor4D(unsigned int const shape_[4], T const *data_) {
         unsigned int size = 1;
         // TODO: 填入正确的 shape 并计算 size
+        for (int i = 0; i < 4; i++) {
+            shape[i] = shape_[i];
+            size *= shape[i];
+        }
         data = new T[size];
         std::memcpy(data, data_, size * sizeof(T));
     }
@@ -28,10 +32,47 @@ struct Tensor4D {
     // 则 `this` 与 `others` 相加时，3 个形状为 `[1, 2, 1, 4]` 的子张量各自与 `others` 对应项相加。
     Tensor4D &operator+=(Tensor4D const &others) {
         // TODO: 实现单向广播的加法
+        // 1.预先计算others 的 strides (步长)，用于将 (n,c,h,w) 坐标转换为线性索引
+        // 线性索引 = n * stride_0 + c * stride_1 + h * stride_2 + w * stride_3
+        unsigned int o_stride3=1;
+        unsigned int o_stride2=others.shape[3];
+        unsigned int o_stride1=o_stride2*others.shape[2];
+        unsigned int o_stride0=o_stride1*others.shape[1];
+        //// 使用指针直接遍历 this->data，避免重复计算 this 的线性索引
+        T* current_ptr = this->data;
+        // 4层循环遍历 this 的所有维度
+        for (unsigned int n = 0; n < shape[0]; ++n) {
+            // 如果 others 在该维度长度为1，则索引固定为0（广播），否则跟随 n
+            unsigned int n_idx = (others.shape[0] == 1) ? 0 : n;
+            
+            for (unsigned int c = 0; c < shape[1]; ++c) {
+                unsigned int c_idx = (others.shape[1] == 1) ? 0 : c;
+                
+                for (unsigned int h = 0; h < shape[2]; ++h) {
+                    unsigned int h_idx = (others.shape[2] == 1) ? 0 : h;
+                    
+                    for (unsigned int w = 0; w < shape[3]; ++w) {
+                        unsigned int w_idx = (others.shape[3] == 1) ? 0 : w;
+                        // 计算 others 中的线性偏移量
+                        unsigned int others_offset = 
+                            n_idx * o_stride0 + 
+                            c_idx * o_stride1 + 
+                            h_idx * o_stride2 + 
+                            w_idx * o_stride3;
+                        // 执行加法
+                        *current_ptr += others.data[others_offset];
+                        
+                        // 移动到 this 的下一个元素
+                        ++current_ptr;
+                    }
+                }
+            }
+        }
         return *this;
     }
 };
 
+
 // ---- 不要修改以下代码 ----
 int main(int argc, char **argv) {
     {
diff --git a/exercises/23_template_const/main.cpp b/exercises/23_template_const/main.cpp
index e0105e168..3e9e0f690 100644
--- a/exercises/23_template_const/main.cpp
+++ b/exercises/23_template_const/main.cpp
@@ -11,6 +11,11 @@ struct Tensor {
     Tensor(unsigned int const shape_[N]) {
         unsigned int size = 1;
         // TODO: 填入正确的 shape 并计算 size
+        for (unsigned int i = 0; i < N; i++)
+        {
+            shape[i] = shape_[i];
+            size *= shape[i];
+        }
         data = new T[size];
         std::memset(data, 0, size * sizeof(T));
     }
@@ -35,6 +40,7 @@ struct Tensor {
         for (unsigned int i = 0; i < N; ++i) {
             ASSERT(indices[i] < shape[i], "Invalid index");
             // TODO: 计算 index
+            index = index * shape[i] + indices[i];
         }
         return index;
     }
diff --git a/exercises/24_std_array/main.cpp b/exercises/24_std_array/main.cpp
index c29718d9d..19d748fd7 100644
--- a/exercises/24_std_array/main.cpp
+++ b/exercises/24_std_array/main.cpp
@@ -4,25 +4,43 @@
 
 // READ: std::array <https://zh.cppreference.com/w/cpp/container/array>
 
+// std::array是对 C 语言风格数组（如 int arr[5]）的现代化封装。
+// - 既保留了原生数组的高性能（零开销）
+// - 又提供了类似 STL 容器（如 std::vector）的安全性和便利性接口。
+// 1.基本语法，需要包含头文件 <array>。
+// - std::array<int, 5> myArray = {1, 2, 3, 4, 5};
+// - 第一个模板参数 int 是数据类型，第二个模板参数 5 是数组大小（必须是编译期常量）。
+// 2.为什么要使用 std::array?
+// - std::array 是一个对象，包含长度消息和数据，不会退化为指针
+// - std::array 支持直接赋值，只要类型和大小相同
+// - std::array 安全性高，提供了 .at() 方法，会进行边界检查。如果越界，会抛出异常
+// - std::array STL兼容性强，提供了迭代器（begin(), end()），可以完美配合 std::sort, std::for_each 等标准算法使用。
+// 3. 主要特性
+// - 内存分配： 与 C 数组一样，数据通常存储在栈（Stack）上（除非它是全局变量或被 new 出来的）。这意味着没有动态内存分配（堆内存）的开销，速度极快。
+// - 固定大小： 大小在编译时必须确定，运行时不能改变（不能像 vector 那样 push_back）。
+// - 零开销： 在优化开启的情况下，std::array 的性能与 C 风格数组完全一致。
+
+// std::memcmp (Memory Compare) 是用来比较两块内存区域的内容是否完全一致的函数
 // TODO: 将下列 `?` 替换为正确的代码
 int main(int argc, char **argv) {
     {
         std::array<int, 5> arr{{1, 2, 3, 4, 5}};
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
+        ASSERT(arr.size() == 5, "Fill in the correct value.");//数组大小
+        ASSERT(sizeof(arr) == 20, "Fill in the correct value.");//int 的大小为 4
         int ans[]{1, 2, 3, 4, 5};
-        ASSERT(std::memcmp(arr.?, ans, ?) == 0, "Fill in the correct values.");
+        //比较arr.data 和 ans，长度为 sizeof(ans)
+        ASSERT(std::memcmp(arr.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");     
     }
     {
         std::array<double, 8> arr;
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
+        ASSERT(arr.size() == 8, "Fill in the correct value.");
+        ASSERT(sizeof(arr) == 64, "Fill in the correct value.");//double 的大小为 8
     }
     {
         std::array<char, 21> arr{"Hello, InfiniTensor!"};
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
-        ASSERT(std::strcmp(arr.?, "Hello, InfiniTensor!") == 0, "Fill in the correct value.");
+        ASSERT(arr.size() == 21, "Fill in the correct value.");
+        ASSERT(sizeof(arr) == 21, "Fill in the correct value.");//char 的大小为 1
+        ASSERT(std::strcmp(arr.data(), "Hello, InfiniTensor!") == 0, "Fill in the correct value.");
     }
     return 0;
 }
diff --git a/exercises/25_std_vector/main.cpp b/exercises/25_std_vector/main.cpp
index f9e41bb78..29bcbcf94 100644
--- a/exercises/25_std_vector/main.cpp
+++ b/exercises/25_std_vector/main.cpp
@@ -3,86 +3,95 @@
 #include <vector>
 
 // READ: std::vector <https://zh.cppreference.com/w/cpp/container/vector>
-
+// vector 是一种序列容器，它允许你在运行时动态地插入和删除元素。需要使用头文件 <vector>。
 // TODO: 将下列 `?` 替换为正确的代码
 int main(int argc, char **argv) {
     {
         std::vector<int> vec{1, 2, 3, 4, 5};
-        ASSERT(vec.size() == ?, "Fill in the correct value.");
+        ASSERT(vec.size() == 5, "Fill in the correct value.");
         // THINK: `std::vector` 的大小是什么意思？与什么有关？
-        ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+        // // 在 64 位系统上，sizeof(vector) 通常是 24 (3个指针)
+        ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         int ans[]{1, 2, 3, 4, 5};
-        ASSERT(std::memcmp(vec.?, ans, sizeof(ans)) == 0, "Fill in the correct values.");
+        ASSERT(std::memcmp(vec.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");
     }
     {
         std::vector<double> vec{1, 2, 3, 4, 5};
         {
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+            ASSERT(vec.size() == 5, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
             double ans[]{1, 2, 3, 4, 5};
-            ASSERT(std::memcmp(vec.?, ans, sizeof(ans)) == 0, "Fill in the correct values.");
+            ASSERT(std::memcmp(vec.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");
         }
         {
-            vec.push_back(6);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
-            vec.pop_back();
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+            vec.push_back(6);// 入栈
+            ASSERT(vec.size() == 6, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
+            vec.pop_back();// 出栈
+            ASSERT(vec.size() == 5, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         }
         {
             vec[4] = 6;
-            ASSERT(vec[0] == ?, "Fill in the correct value.");
-            ASSERT(vec[1] == ?, "Fill in the correct value.");
-            ASSERT(vec[2] == ?, "Fill in the correct value.");
-            ASSERT(vec[3] == ?, "Fill in the correct value.");
-            ASSERT(vec[4] == ?, "Fill in the correct value.");
+            ASSERT(vec[0] == 1, "Fill in the correct value.");
+            ASSERT(vec[1] == 2, "Fill in the correct value.");
+            ASSERT(vec[2] == 3, "Fill in the correct value.");
+            ASSERT(vec[3] == 4, "Fill in the correct value.");
+            ASSERT(vec[4] == 6, "Fill in the correct value.");
         }
         {
             // THINK: `std::vector` 插入删除的时间复杂度是什么？
-            vec.insert(?, 1.5);
+            // insert 插入，在中间或头部插入会导致插入点之后的元素全部向后移动，时间复杂度为 $O(n)$。
+            // - insert 的第一个参数必须是“迭代器”（Iterator），不能是下标。
+            // - 插入单个元素 vec.insert(it+index, element)。;
+            // - 插入多个相同的元素 vec.insert(it+index, count, element)。；
+
+            // auto it=vec.begin();
+            // vec.insert(it+1, 1.5);
+            vec.insert(vec.begin() + 1, 1.5);
             ASSERT((vec == std::vector<double>{1, 1.5, 2, 3, 4, 6}), "Make this assertion pass.");
-            vec.erase(?);
+            vec.erase(vec.begin() + 3);
             ASSERT((vec == std::vector<double>{1, 1.5, 2, 4, 6}), "Make this assertion pass.");
         }
         {
             vec.shrink_to_fit();
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 5, "Fill in the correct value.");
             vec.clear();
-            ASSERT(vec.empty(), "`vec` is empty now.");
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.empty(), "`vec` is empty now.");// empty不改变capacity
+            ASSERT(vec.size() == 0, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 5, "Fill in the correct value.");
         }
     }
     {
-        std::vector<char> vec(?, ?); // TODO: 调用正确的构造函数
+        std::vector<char> vec(48, 'z'); // TODO: 调用正确的构造函数
         ASSERT(vec[0] == 'z', "Make this assertion pass.");
         ASSERT(vec[47] == 'z', "Make this assertion pass.");
         ASSERT(vec.size() == 48, "Make this assertion pass.");
-        ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+        ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         {
-            auto capacity = vec.capacity();
+            // resize改变大小(size)和容量(capacity)
             vec.resize(16);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in a correct identifier.");
+            ASSERT(vec.size() == 16, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 48, "Fill in a correct identifier.");
         }
         {
+            //reserve预留空间，只改变capacity
             vec.reserve(256);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.size() == 16, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 256, "Fill in the correct value.");
         }
         {
             vec.push_back('a');
             vec.push_back('b');
             vec.push_back('c');
             vec.push_back('d');
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
-            ASSERT(vec[15] == ?, "Fill in the correct value.");
-            ASSERT(vec[?] == 'a', "Fill in the correct value.");
-            ASSERT(vec[?] == 'b', "Fill in the correct value.");
-            ASSERT(vec[?] == 'c', "Fill in the correct value.");
-            ASSERT(vec[?] == 'd', "Fill in the correct value.");
+            ASSERT(vec.size() == 20, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 256, "Fill in the correct value.");
+            ASSERT(vec[15] == 'z', "Fill in the correct value.");
+            ASSERT(vec[16] == 'a', "Fill in the correct value.");
+            ASSERT(vec[17] == 'b', "Fill in the correct value.");
+            ASSERT(vec[18] == 'c', "Fill in the correct value.");
+            ASSERT(vec[19] == 'd', "Fill in the correct value.");
         }
     }
 
diff --git a/exercises/26_std_vector_bool/main.cpp b/exercises/26_std_vector_bool/main.cpp
index b4ab4f9c4..15103c20e 100644
--- a/exercises/26_std_vector_bool/main.cpp
+++ b/exercises/26_std_vector_bool/main.cpp
@@ -6,29 +6,29 @@
 
 // TODO: 将下列 `?` 替换为正确的代码
 int main(int argc, char **argv) {
-    std::vector<bool> vec(?, ?);// TODO: 正确调用构造函数
+    std::vector<bool> vec(100, true);// TODO: 正确调用构造函数
     ASSERT(vec[0], "Make this assertion pass.");
     ASSERT(vec[99], "Make this assertion pass.");
     ASSERT(vec.size() == 100, "Make this assertion pass.");
     // NOTICE: 平台相关！注意 CI:Ubuntu 上的值。
     std::cout << "sizeof(std::vector<bool>) = " << sizeof(std::vector<bool>) << std::endl;
-    ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+    ASSERT(sizeof(vec) == 40, "Fill in the correct value.");
     {
         vec[20] = false;
-        ASSERT(?vec[20], "Fill in `vec[20]` or `!vec[20]`.");
+        ASSERT(!vec[20], "Fill in `vec[20]` or `!vec[20]`.");
     }
     {
         vec.push_back(false);
-        ASSERT(vec.size() == ?, "Fill in the correct value.");
-        ASSERT(?vec[100], "Fill in `vec[100]` or `!vec[100]`.");
+        ASSERT(vec.size() == 101, "Fill in the correct value.");
+        ASSERT(!vec[100], "Fill in `vec[100]` or `!vec[100]`.");
     }
     {
         auto ref = vec[30];
-        ASSERT(?ref, "Fill in `ref` or `!ref`");
+        ASSERT(ref, "Fill in `ref` or `!ref`");
         ref = false;
-        ASSERT(?ref, "Fill in `ref` or `!ref`");
+        ASSERT(!ref, "Fill in `ref` or `!ref`");
         // THINK: WHAT and WHY?
-        ASSERT(?vec[30], "Fill in `vec[30]` or `!vec[30]`.");
+        ASSERT(!vec[30], "Fill in `vec[30]` or `!vec[30]`.");
     }
     return 0;
 }
diff --git a/exercises/27_strides/main.cpp b/exercises/27_strides/main.cpp
index baceaf2a9..e190d4a1d 100644
--- a/exercises/27_strides/main.cpp
+++ b/exercises/27_strides/main.cpp
@@ -18,6 +18,16 @@ std::vector<udim> strides(std::vector<udim> const &shape) {
     // TODO: 完成函数体，根据张量形状计算张量连续存储时的步长。
     // READ: 逆向迭代器 std::vector::rbegin <https://zh.cppreference.com/w/cpp/container/vector/rbegin>
     //       使用逆向迭代器可能可以简化代码
+
+    // 这里的逻辑是：从最后一个维度开始向前遍历。
+    // 最后一个维度的步长总是 1（对于连续存储）。
+    // 前一个维度的步长 = 后一个维度的步长 * 后一个维度的形状大小。
+    udim current_stride = 1;
+    for(size_t i = shape.size(); i > 0; --i){
+        // i-1为当前维度索引
+        strides[i - 1] = current_stride;
+        current_stride *= shape[i - 1];
+    }
     return strides;
 }
 
diff --git a/exercises/28_std_string/main.cpp b/exercises/28_std_string/main.cpp
index d8b276274..cf9175d2b 100644
--- a/exercises/28_std_string/main.cpp
+++ b/exercises/28_std_string/main.cpp
@@ -9,10 +9,18 @@ int main(int argc, char **argv) {
     auto hello = "Hello"s;
     auto world = "world";
     // READ: `decltype` 表达式 <https://zh.cppreference.com/w/cpp/language/decltype>
+    // `decltype`意为 "declare type"（声明类型）
+    // - 在编译期推导一个表达式或变量的类型，但不会实际计算表达式的值。
+    // - int a = 10;
+    // - decltype(a) b = 20; // b 的类型是 int，因为 a 是 int
+    // - auto add(int x, double y) -> decltype(x + y); // 推导出返回类型为 double
+
     // READ: `std::is_same_v` 元编程判别 <https://zh.cppreference.com/w/cpp/types/is_same>
-    ASSERT((std::is_same_v<decltype(hello), ?>), "Fill in the missing type.");
-    ASSERT((std::is_same_v<decltype(world), ?>), "Fill in the missing type.");
+    // std::is_same_v 是 C++17 引入的一个模板常量（属于 <type_traits> 头文件）。
+    // - 用于在编译期判断两个类型是否完全相同。
+    ASSERT((std::is_same_v<decltype(hello), std::string>), "Fill in the missing type.");
+    ASSERT((std::is_same_v<decltype(world), const char*>), "Fill in the missing type.");
     // TODO: 将 `?` 替换为正确的字符串
-    ASSERT(hello + ", " + world + '!' == "?", "Fill in the missing string.");
+    ASSERT(hello + ", " + world + '!' == "Hello, world!", "Fill in the missing string.");
     return 0;
 }
diff --git a/exercises/29_std_map/main.cpp b/exercises/29_std_map/main.cpp
index fcccca347..68122a5fc 100644
--- a/exercises/29_std_map/main.cpp
+++ b/exercises/29_std_map/main.cpp
@@ -7,11 +7,13 @@
 template<class k, class v>
 bool key_exists(std::map<k, v> const &map, k const &key) {
     // TODO: 实现函数
+    return map.find(key) != map.end();
 }
 
 template<class k, class v>
 void set(std::map<k, v> &map, k key, v value) {
     // TODO: 实现函数
+    map[key] = value;
 }
 
 // ---- 不要修改以下代码 ----
diff --git a/exercises/30_std_unique_ptr/main.cpp b/exercises/30_std_unique_ptr/main.cpp
index 9b98b5794..26feeef96 100644
--- a/exercises/30_std_unique_ptr/main.cpp
+++ b/exercises/30_std_unique_ptr/main.cpp
@@ -53,8 +53,8 @@ int main(int argc, char **argv) {
         {"fd"},
         // TODO: 分析 problems[1] 中资源的生命周期，将记录填入 `std::vector`
         // NOTICE: 此题结果依赖对象析构逻辑，平台相关，提交时以 CI 实际运行平台为准
-        {"", "", "", "", "", "", "", ""},
-        {"", "", "", "", "", "", "", ""},
+        {"d", "ffr"},
+        {"d", "d","r"},
     };
 
     // ---- 不要修改以下代码 ----
diff --git a/exercises/31_std_shared_ptr/main.cpp b/exercises/31_std_shared_ptr/main.cpp
index febbbcc6f..d35134457 100644
--- a/exercises/31_std_shared_ptr/main.cpp
+++ b/exercises/31_std_shared_ptr/main.cpp
@@ -10,36 +10,36 @@ int main(int argc, char **argv) {
     std::shared_ptr<int> ptrs[]{shared, shared, shared};
 
     std::weak_ptr<int> observer = shared;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 4, "");
 
     ptrs[0].reset();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 3, "");
 
     ptrs[1] = nullptr;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 2, "");
 
     ptrs[2] = std::make_shared<int>(*shared);
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 1, "");
 
     ptrs[0] = shared;
     ptrs[1] = shared;
     ptrs[2] = std::move(shared);
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 3, "");
 
     std::ignore = std::move(ptrs[0]);
     ptrs[1] = std::move(ptrs[1]);
     ptrs[1] = std::move(ptrs[2]);
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 2, "");
 
     shared = observer.lock();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 3, "");
 
     shared = nullptr;
     for (auto &ptr : ptrs) ptr = nullptr;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 0, "");
 
     shared = observer.lock();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 0, "");
 
     return 0;
 }
diff --git a/exercises/32_std_transform/main.cpp b/exercises/32_std_transform/main.cpp
index f4dc25a5c..948953bc0 100644
--- a/exercises/32_std_transform/main.cpp
+++ b/exercises/32_std_transform/main.cpp
@@ -10,6 +10,10 @@ int main(int argc, char **argv) {
     std::vector<int> val{8, 13, 21, 34, 55};
     // TODO: 调用 `std::transform`，将 `v` 中的每个元素乘以 2，并转换为字符串，存入 `ans`
     // std::vector<std::string> ans
+    std::vector<std::string> ans(val.size());
+    std::transform(val.begin(), val.end(), ans.begin(), [](int x) {
+        return std::to_string(x * 2);
+    });
     ASSERT(ans.size() == val.size(), "ans size should be equal to val size");
     ASSERT(ans[0] == "16", "ans[0] should be 16");
     ASSERT(ans[1] == "26", "ans[1] should be 26");
diff --git a/exercises/33_std_accumulate/main.cpp b/exercises/33_std_accumulate/main.cpp
index 6326929d5..caeeccd3c 100644
--- a/exercises/33_std_accumulate/main.cpp
+++ b/exercises/33_std_accumulate/main.cpp
@@ -12,6 +12,7 @@ int main(int argc, char **argv) {
     //       - 连续存储；
     //       的张量占用的字节数
     // int size =
+    int size = std::accumulate(std::begin(shape), std::end(shape), sizeof(DataType), std::multiplies<int>());
     ASSERT(size == 602112, "4x1x3x224x224 = 602112");
     return 0;
 }