Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters.

Example

For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3.

For "bbbbb" the longest substring is "b", with the length of 1.

Notes:

1. Forward two pointers
2. Apply template
3. Use HashSet to judge whether substring contains repeated characters

    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }

        Set<Character> set = new HashSet<>();
        int n = s.length();
        int j = 0;
        int max = 0;

        for (int i = 0; i < n; ++i) {
            while(j < n && !set.contains(s.charAt(j))) {
                set.add(s.charAt(j));
                j++;
            }

            max = Math.max(max, s.substring(i, j).length());
            set.remove(s.charAt(i));
        }

        return max;
    }