public class Solution {
    public int lengthOfLongestSubstring(String s) {
        int left=0,Max=0;
        Map<Character,Integer> map = new HashMap<Character,Integer>();
        char[] chs = s.toCharArray();
        for(int i=0;i<chs.length;i++){
            if(map.containsKey(chs[i]) && map.get(chs[i])>=left){
                left = map.get(chs[i])+1;
            }
            map.put(chs[i],i);
            Max = Max>(i-left+1)?Max:(i-left+1);
        }
        return Max;
    }
}

C语言源代码：

#include<limits.h>
#include<stdio.h>
int lengthOfLongestSubstring(char* s) {
    int i,j,left=0,Max=0,hash[256];
    for(j=0;j<256;j++)hash[j]=INT_MAX;
    for(i=0;s[i];i++){
        if(hash[s[i]]!=INT_MAX && hash[s[i]]>=left)
            left=hash[s[i]]+1;
        hash[s[i]]=i;
        Max = Max>(i-left+1)?Max:(i-left+1);
    }
    return Max;
}

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int Max=0,left=0;
        map<int,int> map;
        for(int i=0;i<s.size();i++){
            std::map<int,int>::iterator iter=map.find(s[i]);
            if(iter!=map.end() && iter->second >=left){
                left=iter->second+1;
            }
            map[s[i]]=i;
            Max = Max>(i-left+1)?Max:(i-left+1);
        }
        return Max;
    }
};

class Solution:
    # @param {string} s
    # @return {integer}
    def lengthOfLongestSubstring(self, s):
        left=0
        Max=0
        hash={}
        for i in range(len(s)):
            ch = s[i]
            if hash.has_key(ch) and hash[ch]>=left:
                left=hash[ch]+1
            hash[ch]=i
            Max= Max if Max>i-left+1 else i-left+1
        return Max