longestsubstring.java

// Given a string s, find the length of the longest substring without repeating characters.
// Input: s = "abcabcbb"
// Output: 3
// Explanation: The answer is "abc", with the length of 3.

//SLIDING WINDOW METHOD
import java.util.*;
import  java.lang.Math.*;
public class longestsubstring {
    public static int lengthOfLongestSubstring(String s) {
        int n = s.length();
        Set<Character> set = new HashSet<>();
        int ans = 0, i = 0, j = 0;
        while (i < n && j < n) {
            // try to extend the range [i, j]
            if (!set.contains(s.charAt(j))){
                set.add(s.charAt(j++));
                ans = Math.max(ans, j - i);
            }
            else {
                set.remove(s.charAt(i++));
            }
        }
        return ans;
    }

    public static void main(String[] args){
        System.out.println(lengthOfLongestSubstring("abccabcbb"));
    }
}