class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.size();
        map<int, int> mp;
        int ans = 0;
        int i = 0, j = 0;
        while(i < n && j < n) {
            if(mp[s[j]] == 0) {
                mp[s[j]] ++;
                ans = max(ans, j - i + 1);
                ++ j;
            }else {
                mp[s[i]] --;
                ++ i;
            }
        }
        return ans;
    }
};