0003_Longest Substring Without Repeating Characters.java

class Solution 
{
    public int lengthOfLongestSubstring(String s) 
    {
        int i = 0, j = 0, max = 0;
        Set<Character> set = new HashSet<>();
        while (j < s.length()) 
        {
            if (!set.contains(s.charAt(j))) 
            {
                set.add(s.charAt(j++));
                max = Math.max(max, set.size());
            } 
            else set.remove(s.charAt(i++));
        }
        return max;
    }
}