3. Longest Substring Without Repeating Characters

class Solution {
    public int lengthOfLongestSubstring(String s) {
        HashMap<Character, Integer> map = new HashMap<>();

        int maxLen = 0;
        for (int i = 0, j = 0; i < s.length(); i++) {
            if (map.containsKey(s.charAt(i))) {
                j = Math.max(j, map.get(s.charAt(i)) + 1);
            }
            map.put(s.charAt(i), i);
            maxLen = Math.max(maxLen, i - j + 1);
        }

        return maxLen;
    }
}