How To Find Longest Substring Without Repeating Characters In Java?

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Java Program To Find Longest Substring Without Repeating Characters In Java :-

Going to write a java program  to find the longest substring without repeating characters in a given string. For example, if  user input “Tutorialspoint4all.com”  as a input string, then the longest substring without repeating or duplicate characters is “Tutorialsp” and its length is 10.

 

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Java Program To Find Longest Substring Without Repeating Characters :-

 

/*Java Program to find longest substring without repeating characters*/

import java.util.*;
import java.util.HashSet;

public class Main {
    public static String longestSubstring(String Input_String){

        HashSet<Character> set = new HashSet<Character>();

        String longestOverAll = "";
        String longestTillNow = "";

        for (int j = 0; j < Input_String.length(); j++) {
            char c = Input_String.charAt(j);

            if (set.contains(c)) {
                longestTillNow = "";
                set.clear();
            }
            longestTillNow += c;
            set.add(c);
            if (longestTillNow.length() > longestOverAll.length()) {
                longestOverAll = longestTillNow;
            }
        }

        return longestOverAll;
    }




public static int lengthOfLongestSubstring(String Input_String) {
        int len = Input_String.length();
        Set<Character> set = new HashSet<>();
        int substring_length = 0, i = 0, j = 0;
       
        while (i < len && j < len) {
            // try to extend the range [i, j]
            if (!set.contains(Input_String.charAt(j))){
                set.add(Input_String.charAt(j++));
                substring_length = Math.max(substring_length, j - i);
            }
            else {
                set.remove(Input_String.charAt(i++));
            }

        }   

        return substring_length;
    }
    public static void main(String[] args) {
        System.out.println("Enter your Input String: ");
        Scanner scanner = new Scanner(System.in);
        String Input_String = scanner.nextLine();
        System.out.println("Your Longest String is " + Input_String);
        System.out.println("The longest Substring Length is : - " + lengthOfLongestSubstring(Input_String));
        System.out.println("The longest Substring is :- "+ longestSubstring(Input_String));

    }
}

 

Output:-

 

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