soln.cpp

// https://leetcode.com/problems/longest-substring-without-repeating-characters/
#define  um unordered_map

int solve (string s) {
        um <char, int> ump;
        int left = 0, right = 0;
        int maxlen = 0;
        int cnt = 0;
        while (right < s.length()) {
            ump[s[right]]++;
            if (ump[s[right]] > 1) {
                cnt++;
            }
            right++;
            if (cnt == 0 && right - left > maxlen) {
                maxlen = right - left;
            }
            while (cnt > 0 && left < right) {
                ump[s[left]]--;
                if (ump[s[left]] == 1) {
                    cnt--;
                }
                left++;
            }
            
        }
        return maxlen;
}