//"最长连续不重复子序列"的哈希解法

class Solution {
public:
    int longestSubstringWithoutDuplication(string s) {
        unordered_map<char,int> count; 
        int res = 0;
        for(int i=0,j=0;i<s.size();i++){
            count[s[i]]++;
            while(j<i && count[s[i]] > 1){
                count[s[j]]--;
                j++;
            }
            res = max(res,i-j+1);
        }
        return res;
    }
};