Merge branch 'doocs:main' into main

Author: Nothing-avil

images/starcharts.svg

@@ -85,8 +85,7 @@ class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
         d = {}
         for i, x in enumerate(nums):
-            y = target - x
-            if y in d:
+            if (y := target - x) in d:
                 return [d[y], i]
             d[x] = i
 ```

solution/0000-0099/0001.Two Sum/README.md

@@ -82,8 +82,7 @@ class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
         d = {}
         for i, x in enumerate(nums):
-            y = target - x
-            if y in d:
+            if (y := target - x) in d:
                 return [d[y], i]
             d[x] = i
 ```

solution/0000-0099/0001.Two Sum/README_EN.md

@@ -2,7 +2,6 @@ class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
         d = {}
         for i, x in enumerate(nums):
-            y = target - x
-            if y in d:
+            if (y := target - x) in d:
                 return [d[y], i]
             d[x] = i

solution/0000-0099/0001.Two Sum/Solution.py

@@ -26,7 +26,7 @@ tags:
 
 <pre>
 <strong>输入: </strong>s = "abcabcbb"
-<strong>输出: </strong>3 
+<strong>输出: </strong>3
 <strong>解释:</strong> 因为无重复字符的最长子串是 <code>"abc"</code>，所以其长度为 3。
 </pre>
 
@@ -62,26 +62,15 @@ tags:
 
 <!-- solution:start -->
 
-### 方法一：双指针 + 哈希表
-
-定义一个哈希表记录当前窗口内出现的字符，记 $i$ 和 $j$ 分别表示不重复子串的开始位置和结束位置，无重复字符子串的最大长度记为 `ans`。
+### 方法一：滑动窗口
 
-遍历字符串 `s` 的每个字符 $s[j]$，我们记为 $c$。若 $s[i..j-1]$ 窗口内存在 $c$，则 $i$ 循环向右移动，更新哈希表，直至 $s[i..j-1]$ 窗口不存在 `c`，循环结束。将 `c` 加入哈希表中，此时 $s[i..j]$ 窗口内不含重复元素，更新 `ans` 的最大值。
+我们可以用两个指针 $l$ 和 $r$ 维护一个滑动窗口，使其始终满足窗口内没有重复字符，初始时 $l$ 和 $r$ 都指向字符串的第一个字符。用一个哈希表或者长度为 $128$ 的数组 $\textit{cnt}$ 来记录每个字符出现的次数，其中 $\textit{cnt}[c]$ 表示字符 $c$ 出现的次数。
 
-最后返回 `ans` 即可。
+接下来，我们依次移动右指针 $r$，每次移动时，将 $\textit{cnt}[s[r]]$ 的值加 $1$，然后判断当前窗口 $[l, r]$ 内 $\textit{cnt}[s[r]]$ 是否大于 $1$，如果大于 $1$，说明当前窗口内有重复字符，我们需要移动左指针 $l$，直到窗口内没有重复字符为止。然后，我们更新答案 $\textit{ans} = \max(\textit{ans}, r - l + 1)$。
 
-时间复杂度 $O(n)$，其中 $n$ 表示字符串 `s` 的长度。
+最终，我们返回答案 $\textit{ans}$ 即可。
 
-双指针算法模板：
-
-```java
-for (int i = 0, j = 0; i < n; ++i) {
-    while (j < i && check(j, i)) {
-        ++j;
-    }
-    // 具体问题的逻辑
-}
-```
+时间复杂度 $O(n)$，其中 $n$ 为字符串的长度。空间复杂度 $O(|\Sigma|)$，其中 $\Sigma$ 表示字符集，这里 $\Sigma$ 的大小为 $128$。
 
 <!-- tabs:start -->
 
@@ -90,14 +79,14 @@ for (int i = 0, j = 0; i < n; ++i) {
 ```python
 class Solution:
     def lengthOfLongestSubstring(self, s: str) -> int:
-        ss = set()
-        ans = i = 0
-        for j, c in enumerate(s):
-            while c in ss:
-                ss.remove(s[i])
-                i += 1
-            ss.add(c)
-            ans = max(ans, j - i + 1)
+        cnt = Counter()
+        ans = l = 0
+        for r, c in enumerate(s):
+            cnt[c] += 1
+            while cnt[c] > 1:
+                cnt[s[l]] -= 1
+                l += 1
+            ans = max(ans, r - l + 1)
         return ans
 ```
 
@@ -106,15 +95,15 @@ class Solution:
 ```java
 class Solution {
     public int lengthOfLongestSubstring(String s) {
-        boolean[] ss = new boolean[128];
-        int ans = 0;
-        for (int i = 0, j = 0; j < s.length(); ++j) {
-            char c = s.charAt(j);
-            while (ss[c]) {
-                ss[s.charAt(i++)] = false;
+        int[] cnt = new int[128];
+        int ans = 0, n = s.length();
+        for (int l = 0, r = 0; r < n; ++r) {
+            char c = s.charAt(r);
+            ++cnt[c];
+            while (cnt[c] > 1) {
+                --cnt[s.charAt(l++)];
             }
-            ss[c] = true;
-            ans = Math.max(ans, j - i + 1);
+            ans = Math.max(ans, r - l + 1);
         }
         return ans;
     }
@@ -127,14 +116,14 @@ class Solution {
 class Solution {
 public:
     int lengthOfLongestSubstring(string s) {
-        bool ss[128]{};
-        int ans = 0;
-        for (int i = 0, j = 0; j < s.size(); ++j) {
-            while (ss[s[j]]) {
-                ss[s[i++]] = false;
+        int cnt[128]{};
+        int ans = 0, n = s.size();
+        for (int l = 0, r = 0; r < n; ++r) {
+            ++cnt[s[r]];
+            while (cnt[s[r]] > 1) {
+                --cnt[s[l++]];
             }
-            ss[s[j]] = true;
-            ans = max(ans, j - i + 1);
+            ans = max(ans, r - l + 1);
         }
         return ans;
     }
@@ -145,14 +134,15 @@ public:
 
 ```go
 func lengthOfLongestSubstring(s string) (ans int) {
-	ss := [128]bool{}
-	for i, j := 0, 0; j < len(s); j++ {
-		for ss[s[j]] {
-			ss[s[i]] = false
-			i++
+	cnt := [128]int{}
+	l := 0
+	for r, c := range s {
+		cnt[c]++
+		for cnt[c] > 1 {
+			cnt[s[l]]--
+			l++
 		}
-		ss[s[j]] = true
-		ans = max(ans, j-i+1)
+		ans = max(ans, r-l+1)
 	}
 	return
 }
@@ -163,13 +153,15 @@ func lengthOfLongestSubstring(s string) (ans int) {
 ```ts
 function lengthOfLongestSubstring(s: string): number {
     let ans = 0;
-    const ss: Set<string> = new Set();
-    for (let i = 0, j = 0; j < s.length; ++j) {
-        while (ss.has(s[j])) {
-            ss.delete(s[i++]);
+    const cnt = new Map<string, number>();
+    const n = s.length;
+    for (let l = 0, r = 0; r < n; ++r) {
+        cnt.set(s[r], (cnt.get(s[r]) || 0) + 1);
+        while (cnt.get(s[r])! > 1) {
+            cnt.set(s[l], cnt.get(s[l])! - 1);
+            ++l;
         }
-        ss.add(s[j]);
-        ans = Math.max(ans, j - i + 1);
+        ans = Math.max(ans, r - l + 1);
     }
     return ans;
 }
@@ -178,24 +170,22 @@ function lengthOfLongestSubstring(s: string): number {
 #### Rust
 
 ```rust
-use std::collections::HashSet;
-
 impl Solution {
     pub fn length_of_longest_substring(s: String) -> i32 {
-        let s = s.as_bytes();
-        let mut ss = HashSet::new();
-        let mut i = 0;
-        s.iter()
-            .map(|c| {
-                while ss.contains(&c) {
-                    ss.remove(&s[i]);
-                    i += 1;
-                }
-                ss.insert(c);
-                ss.len()
-            })
-            .max()
-            .unwrap_or(0) as i32
+        let mut cnt = [0; 128];
+        let mut ans = 0;
+        let mut l = 0;
+        let chars: Vec<char> = s.chars().collect();
+        let n = chars.len();
+        for (r, &c) in chars.iter().enumerate() {
+            cnt[c as usize] += 1;
+            while cnt[c as usize] > 1 {
+                cnt[chars[l] as usize] -= 1;
+                l += 1;
+            }
+            ans = ans.max((r - l + 1) as i32);
+        }
+        ans
     }
 }
 ```
@@ -209,13 +199,15 @@ impl Solution {
  */
 var lengthOfLongestSubstring = function (s) {
     let ans = 0;
-    const ss = new Set();
-    for (let i = 0, j = 0; j < s.length; ++j) {
-        while (ss.has(s[j])) {
-            ss.delete(s[i++]);
+    const n = s.length;
+    const cnt = new Map();
+    for (let l = 0, r = 0; r < n; ++r) {
+        cnt.set(s[r], (cnt.get(s[r]) || 0) + 1);
+        while (cnt.get(s[r]) > 1) {
+            cnt.set(s[l], cnt.get(s[l]) - 1);
+            ++l;
         }
-        ss.add(s[j]);
-        ans = Math.max(ans, j - i + 1);
+        ans = Math.max(ans, r - l + 1);
     }
     return ans;
 };
@@ -226,14 +218,15 @@ var lengthOfLongestSubstring = function (s) {
 ```cs
 public class Solution {
     public int LengthOfLongestSubstring(string s) {
+        int n = s.Length;
         int ans = 0;
-        var ss = new HashSet<char>();
-        for (int i = 0, j = 0; j < s.Length; ++j) {
-            while (ss.Contains(s[j])) {
-                ss.Remove(s[i++]);
+        var cnt = new int[128];
+        for (int l = 0, r = 0; r < n; ++r) {
+            ++cnt[s[r]];
+            while (cnt[s[r]] > 1) {
+                --cnt[s[l++]];
             }
-            ss.Add(s[j]);
-            ans = Math.Max(ans, j - i + 1);
+            ans = Math.Max(ans, r - l + 1);
         }
         return ans;
     }
@@ -244,19 +237,18 @@ public class Solution {
 
 ```php
 class Solution {
-    /**
-     * @param String $s
-     * @return Integer
-     */
     function lengthOfLongestSubstring($s) {
+        $n = strlen($s);
         $ans = 0;
-        $ss = [];
-        for ($i = 0, $j = 0; $j < strlen($s); ++$j) {
-            while (in_array($s[$j], $ss)) {
-                unset($ss[array_search($s[$i++], $ss)]);
+        $cnt = array_fill(0, 128, 0);
+        $l = 0;
+        for ($r = 0; $r < $n; ++$r) {
+            $cnt[ord($s[$r])]++;
+            while ($cnt[ord($s[$r])] > 1) {
+                $cnt[ord($s[$l])]--;
+                $l++;
             }
-            $ss[] = $s[$j];
-            $ans = max($ans, $j - $i + 1);
+            $ans = max($ans, $r - $l + 1);
         }
         return $ans;
     }
@@ -268,62 +260,40 @@ class Solution {
 ```swift
 class Solution {
     func lengthOfLongestSubstring(_ s: String) -> Int {
-        var map = [Character: Int]()
-        var currentStartingIndex = 0
-        var i = 0
-        var maxLength = 0
-        for char in s {
-            if map[char] != nil {
-                if map[char]! >= currentStartingIndex {
-                    maxLength = max(maxLength, i - currentStartingIndex)
-                    currentStartingIndex = map[char]! + 1
-                }
+        let n = s.count
+        var ans = 0
+        var cnt = [Int](repeating: 0, count: 128)
+        var l = 0
+        let sArray = Array(s)
+        for r in 0..<n {
+            cnt[Int(sArray[r].asciiValue!)] += 1
+            while cnt[Int(sArray[r].asciiValue!)] > 1 {
+                cnt[Int(sArray[l].asciiValue!)] -= 1
+                l += 1
             }
-            map[char] = i
-            i += 1
+            ans = max(ans, r - l + 1)
         }
-        return max(maxLength, i - currentStartingIndex)
+        return ans
     }
 }
 ```
 
-#### Nim
-
-```nim
-proc lengthOfLongestSubstring(s: string): int =
-  var
-    i = 0
-    j = 0
-    res = 0
-    literals: set[char] = {}
-
-  while i < s.len:
-    while s[i] in literals:
-      if s[j] in literals:
-        excl(literals, s[j])
-      j += 1
-    literals.incl(s[i]) # Uniform Function Call Syntax f(x) = x.f
-    res = max(res, i - j + 1)
-    i += 1
-
-  result = res # result has the default return value
-```
-
 #### Kotlin
 
 ```kotlin
 class Solution {
     fun lengthOfLongestSubstring(s: String): Int {
-        var char_set = BooleanArray(128)
-        var left = 0
+        val n = s.length
         var ans = 0
-        s.forEachIndexed { right, c ->
-            while (char_set[c.code]) {
-                char_set[s[left].code] = false
-                left++
+        val cnt = IntArray(128)
+        var l = 0
+        for (r in 0 until n) {
+            cnt[s[r].toInt()]++
+            while (cnt[s[r].toInt()] > 1) {
+                cnt[s[l].toInt()]--
+                l++
             }
-            char_set[c.code] = true
-            ans = Math.max(ans, right - left + 1)
+            ans = Math.max(ans, r - l + 1)
         }
         return ans
     }