Longest Substring Without Repeating Characters.java

  public int lengthOfLongestSubString(String s) {
    int n = s.length();
    Set<Character> set = new HashSet<>();
    int ans = 0, i = 0, j = 0;
    while (i < n && j < n) {
      if (!set.contains(s.charAt(j))) {
        set.add(s.charAt(j));
        j++;
        ans = Math.max(ans, j - i);
      } else {
        set.remove(s.charAt(i));
        i++;
      }
    }
    return ans;
  }