AcWing——61. 最长不含重复字符的子字符串

双指针解法

class Solution {
public:
    int longestSubstringWithoutDuplication(string s) {
        unordered_map<char, int> hash;  //hash['x'] = 1;
        int ans = 0;
        for(int i = 0, j = 0; j < (int)s.size(); ++j){
            hash[s[j]]++; //hash['a']++; 0 1 2
           while(hash[s[j]] > 1){  //        dbfg
               hash[s[i++]]--;     //dbfg       ij 
           }
           ans = max(ans, j - i + 1);
        }
        return ans;
    }
};