Longest Distinct characters in string Java

PROGRAM TO FIND THE LENGTH OF THE LONGEST SUBSTRING WITHOUT REPEATING CHARACTERS

import java.util.*;

  

public class MAIN {

  

    static final int NO_OF_CHARS = 256;

  

    static int longestUniqueSubsttr(String str)

    {

        int n = str.length();

  

        int res = 0; // result

  

        // last index of all characters is initialized

        // as -1

        int [] lastIndex = new int[NO_OF_CHARS];

        Arrays.fill(lastIndex, -1);

  

        // Initialize start of current window

        int i = 0;

  

        // Move end of current window

        for (int j = 0; j < n; j++) {

  

            // Find the last index of str[j]

            // Update i (starting index of current window)

            // as maximum of current value of i and last

            // index plus 1

            i = Math.max(i, lastIndex[str.charAt(j)] + 1);

  

            // Update result if we get a larger window

            res = Math.max(res, j - i + 1);

  

            // Update last index of j.

            lastIndex[str.charAt(j)] = j;

        }

        return res;

    }

  

    /* Driver program to test above function */

    public static void main(String[] args)

    {

        String str = "geeksforgeeks";

        System.out.println("The input string is " + str);

        int len = longestUniqueSubsttr(str);

        System.out.println("The length of "

                           + "the longest non repeating character is " + len);

    }

}




OUTPUT

The input string is geeksforgeeks
The length of the longest non-repeating character substring is 7

CREDITS: https://www.geeksforgeeks.org/length-of-the-longest-substring-without-repeating-characters/