3 - Longest Substring Without Repeating Characters

 C++

• class Solution {
  public:
      int lengthOfLongestSubstring(string s) {
          unordered_set<char> ss;
          int i = 0, ans = 0;
          for (int j = 0; j < s.size(); ++j) {
              while (ss.count(s[j])) ss.erase(s[i++]);
              ss.insert(s[j]);
              ans = max(ans, j - i + 1);
          }
          return ans;
      }
  };