leetcode 003 Longest Substring Without Repeating Characters(java)

最新推荐文章于 2025-08-13 21:50:19 发布

原创最新推荐文章于 2025-08-13 21:50:19 发布 · 300 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#leetcode

leetcode 专栏收录该内容

7 篇文章

订阅专栏

本文介绍了一种使用HashMap来解决LeetCode上一道中等难度题目的方法：寻找字符串中最长的无重复字符子串。通过不断更新起始位置和记录最长子串长度的方式，实现高效查找。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Longest Substring Without Repeating Characters

My Submissions

Total Accepted: 111400 Total Submissions: 532861 Difficulty: Medium

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

题意：求最长连续不重复子序列，和字典序没关系！！！！不能习惯leetcode测试数据给的太少，刚开始把题意理解错了。哎，英文太烂。

用HashMap很好解。出现重复的字母更新一下start就好。

import java.util.HashMap;
import java.util.Scanner;


public class Solution {
    public static int lengthOfLongestSubstring(String s) {
        int ans=0;
        int start=0;
        int i=0;
        HashMap<Character, Integer> map=new HashMap<Character, Integer>();
        
        for(i=0;i<s.length();i++){
            char c=s.charAt(i);
            if(map.containsKey(c)&&start<=map.get(c)){
                ans=Math.max(ans, i-start);
                start=map.get(c)+1;
                map.put(c, i);
            }
            else{
                map.put(c, i);
            }
            
        }
        return Math.max(ans, i-start);
    }  
    
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        while(true){
            String tmp=scanner.next();
            System.out.println(lengthOfLongestSubstring(tmp));
        }
    }
}