四刷3

Author: diguage

docs/0003-longest-substring-without-repeating-characters.adoc

@@ -1,38 +1,41 @@
 
 [#0003-longest-substring-without-repeating-characters]
-= 3. Longest Substring Without Repeating Characters
+= 3. 无重复字符的最长子串
 
-{leetcode}/problems/longest-substring-without-repeating-characters/[LeetCode - Longest Substring Without Repeating Characters^]
+https://leetcode.cn/problems/longest-substring-without-repeating-characters/[LeetCode - 3. 无重复字符的最长子串 ^]
 
-Given a string, find the length of the *longest substring* without repeating characters.
+给定一个字符串 `s` ，请你找出其中不含有重复字符的 **最长子串** 的长度。
 
+*示例 1:*
 
-.Example 1:
-[subs="verbatim,quotes,macros"]
-----
-*Input:* "abcabcbb"
-*Output:* 3 
-*Explanation:* The answer is `"abc"`, with the length of 3. 
-----
+....
+输入: s = "abcabcbb"
+输出: 3
+解释: 因为无重复字符的最长子串是 "abc"，所以其长度为 3。
+....
 
+*示例 2:*
 
-.Example 2:
-[subs="verbatim,quotes,macros"]
-----
-*Input:* "bbbbb"
-*Output:* 1
-*Explanation:* The answer is `"b"`, with the length of 1.
-----
+....
+输入: s = "bbbbb"
+输出: 1
+解释: 因为无重复字符的最长子串是 "b"，所以其长度为 1。
+....
 
+*示例 3:*
 
-.Example 3:
-[subs="verbatim,quotes,macros"]
-----
-*Input:* "pwwkew"
-*Output:* 3
-*Explanation:* The answer is `"wke"`, with the length of 3. 
-             Note that the answer must be a *substring*, `"pwke"` is a _subsequence_ and not a substring.
-----
+....
+输入: s = "pwwkew"
+输出: 3
+解释: 因为无重复字符的最长子串是 "wke"，所以其长度为 3。
+     请注意，你的答案必须是 子串 的长度，"pwke" 是一个子序列，不是子串。
+....
+
+
+*提示：*
+
+* `0 \<= s.length \<= 5 * 10^4^`
+* `s` 由英文字母、数字、符号和空格组成
 
 == 思路分析
 
@@ -90,6 +93,15 @@ include::{sourcedir}/_0003_LongestSubstringWithoutRepeatingCharacters_2.java[tag
 include::{sourcedir}/_0003_LongestSubstringWithoutRepeatingCharacters_3.java[tag=answer]
 ----
 --
+
+四刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0003_LongestSubstringWithoutRepeatingCharacters_4.java[tag=answer]
+----
+--
 ====
 
 == 参考资料

logbook/202503.adoc

@@ -100,6 +100,11 @@ endif::[]
 |{doc_base_url}/0124-binary-tree-maximum-path-sum.adoc[题解]
 |⭕️ 深度优先搜索，注意处理负数情况
 
+|{counter:codes2503}
+|{leetcode_base_url}/longest-substring-without-repeating-characters/[3. 无重复字符的最长子串^]
+|{doc_base_url}/0003-longest-substring-without-repeating-characters.adoc[题解]
+|✅ 滑动窗口
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

src/main/java/com/diguage/algo/leetcode/_0003_LongestSubstringWithoutRepeatingCharacters_4.java

@@ -0,0 +1,48 @@
+package com.diguage.algo.leetcode;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class _0003_LongestSubstringWithoutRepeatingCharacters_4 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-01 17:03:21
+   */
+  public int lengthOfLongestSubstring(String s) {
+    if (s == null || s.isEmpty()) {
+      return 0;
+    }
+    int result = 0;
+    Map<Character, Integer> counter = new HashMap<>();
+    int left = 0, right = 0;
+    char[] chars = s.toCharArray();
+    while (right < chars.length) {
+      char rc = chars[right];
+      right++;
+      int cnt = counter.getOrDefault(rc, 0) + 1;
+      counter.put(rc, cnt);
+      if (cnt == 1) {
+        // 这里使用 right - left (right已经++了)更好
+        result = Math.max(result, counter.size());
+      }
+      while (left < chars.length && counter.get(rc) > 1) {
+        char lc = chars[left];
+        left++;
+        int nc = counter.get(lc) - 1;
+        if (nc == 0) {
+          counter.remove(lc);
+        } else {
+          counter.put(lc, nc);
+        }
+      }
+    }
+    return result;
+  }
+  // end::answer[]
+
+  public static void main(String[] args) {
+    new _0003_LongestSubstringWithoutRepeatingCharacters_4()
+      .lengthOfLongestSubstring("pwwkew");
+  }
+}