[LeetCode]Longest Substring Without Repeating Characters

最新推荐文章于 2025-05-18 01:04:12 发布

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本文介绍了一种寻找字符串中最长无重复字符子串的方法，使用双指针技术和哈希表来跟踪字符位置，实现高效的查找过程。

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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.

两个指针，采用hash记录出现字母的位置。

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        vector<int>hash (300,-1);
        int i,j;
        i=0;
        j=0;
        if(s.size()==0)
            return 0;
        if(s.size()==1)
            return 1;
        int ret=0;
        while(i<=j && j<s.length()){
            if(hash[s[j]]!=-1){
                for(;i<hash[s[j]];++i){
                    hash[s[i]] = -1;
                }
                i = hash[s[j]]+1;
                hash[s[j]]=j;
            }
            else{
                hash[s[j]]=j;
            }
            ret = max(ret,j-i+1);
            ++j;
        }
        return ret;
    }
    
};