longest-substring-without-repeating-characters.java

class Solution {
    public int lengthOfLongestSubstring(String s) {
        Set<Character> ss = new HashSet<>();
        int i = 0, ans = 0;
        for (int j = 0; j < s.length(); ++j) {
            char c = s.charAt(j);
            while (ss.contains(c)) {
                ss.remove(s.charAt(i++));
            }
            ss.add(c);
            ans = Math.max(ans, j - i + 1);
        }
        return ans;
    }
}