Complete all C++ exercises with optimizations

Author: zinc

exercises/00_hello_world/main.cpp

@@ -6,6 +6,6 @@
 
 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;
     return 0;
 }

exercises/01_variable&add/main.cpp

@@ -4,7 +4,7 @@
 
 int main(int argc, char **argv) {
     // TODO: 补全变量定义并打印加法运算
-    // x ?
+    int x = 42;
     std::cout << x << " + " << x << " = " << x + x << std::endl;
     return 0;
 }

exercises/02_function/main.cpp

@@ -5,6 +5,7 @@
 // NOTICE: 补充由内而外读法的机翻解释 <https://learn.microsoft.com/zh-cn/cpp/c-language/interpreting-more-complex-declarators?view=msvc-170>
 
 // 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 +17,5 @@ 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;
 }

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;
 }

exercises/04_static/main.cpp

@@ -10,10 +10,10 @@ 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;
 }

exercises/05_constexpr/main.cpp

@@ -1,14 +1,21 @@
 #include "../exercise.h"
 
+// 使用迭代实现斐波那契数列，时间复杂度O(n)
 constexpr unsigned long long fibonacci(int i) {
-    switch (i) {
-        case 0:
-            return 0;
-        case 1:
-            return 1;
-        default:
-            return fibonacci(i - 1) + fibonacci(i - 2);
+    if (i == 0) return 0;
+    if (i == 1) return 1;
+    
+    unsigned long long a = 0;
+    unsigned long long b = 1;
+    unsigned long long c = 0;
+    
+    for (int j = 2; j <= i; ++j) {
+        c = a + b;
+        a = b;
+        b = c;
     }
+    
+    return b;
 }
 
 int main(int argc, char **argv) {
@@ -19,7 +26,7 @@ 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);
+    const auto ANS = fibonacci(ANS_N);
     std::cout << "fibonacci(" << ANS_N << ") = " << ANS << std::endl;
 
     return 0;

exercises/06_array/main.cpp

@@ -1,4 +1,4 @@
-#include "../exercise.h"
+#include "../exercise.h"
 
 // READ: 数组 <https://zh.cppreference.com/w/cpp/language/array>
 
@@ -11,13 +11,13 @@ 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");
+    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");

exercises/07_loop/main.cpp

@@ -5,10 +5,11 @@
 // 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};
+    static int cached = 1;
     // TODO: 设置正确的循环条件
-    for (; false; ++cached) {
-        cache[cached] = cache[cached - 1] + cache[cached - 2];
+    for (; cached < i; ++cached) {
+        cache[cached + 1] = cache[cached] + cache[cached - 1];
     }
     return cache[i];
 }

exercises/08_pointer/main.cpp

@@ -1,10 +1,16 @@
-#include "../exercise.h"
+#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) {
     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 *p = ptr + i * stride;
+        if (*(p + 2 * stride) != *p + *(p + stride)) {
+            return false;
+        }
+    }
     return true;
 }
 

exercises/09_enum&union/main.cpp

@@ -36,7 +36,7 @@ ColorEnum convert_by_pun(Color c) {
     };
 
     TypePun pun;
-    // TODO: 补全类型双关转换
+    pun.c = c;
 
     return pun.e;
 }