package question;

import java.util.HashSet;
import java.util.Set;

public class Question3 {

 public static void main(String[] args) {
 String s = "au";
 System.out.println(new Question3().lengthOfLongestSubstring(s));
 }

 public int lengthOfLongestSubstring(String s) {
 if (s == null || s.length() == 0) return 0;
 char[] chars = s.toCharArray();
 int left = 0;
 int right = 0;
 int max = 0;
 Set<Character> set = new HashSet<>();
 while (right < chars.length) {
 if (set.contains(chars[right])) {
 set.remove(chars[left]);
 left++;
 } else {
 set.add(chars[right]);
 right++;
 }
 max = Math.max(max, set.size());
 }
 return max;
 }
}