3. 无重复字符的最长子串 Longest Substring Without Repeating Characters

最新推荐文章于 2025-07-22 14:38:58 发布

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本文详细解析了如何寻找字符串中最长的无重复字符子串，并提供了具体实现的代码示例。通过使用HashMap数据结构，算法能有效地跟踪每个字符的最新位置，从而避免重复并计算出最长无重复子串的长度。

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Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.

class Solution {
    public int lengthOfLongestSubstring(String s) {
        if(s.length() == 0) return 0;
        HashMap<Character,Integer> map = new HashMap<>();
        int length = 0;
        for(int i = 0 , j = 0; i< s.length(); i++){
            if(map.containsKey(s.charAt(i))){
                j =Math.max(j,map.get(s.charAt(i)) + 1) ;
        
                
            }
            map.put(s.charAt(i),i);
            length = Math.max(length, i - j + 1);
            
        }
        return length;
    }
}