ReturnSubsequence.java

package Others;

import java.util.Scanner;

public class ReturnSubsequence {
    public static void main(String[] args) {
        System.out.println("Enter String: ");
        Scanner s = new Scanner(System.in);
        String givenString = s.next(); //given string
        String[] subsequence = returnSubsequence(givenString); //calling returnSubsequence() function
        System.out.println("Subsequences : ");
        //print the given array of subsequences
        for (int i = 0; i < subsequence.length; i++) {
            System.out.println(subsequence[i]);
        }
        s.close();
    }

    /**
     * @param givenString
     * @return subsequence
     */
    private static String[] returnSubsequence(String givenString) {
        if (givenString.length() == 0) // If string is empty we will create an array of size=1 and insert "" (Empty string) in it
        {
            String[] ans = new String[1];
            ans[0] = "";
            return ans;

        }
        String[] SmallAns = returnSubsequence(givenString.substring(1)); //recursive call to get subsequences of substring starting from index position=1

        String[] ans = new String[2 * SmallAns.length];// Our answer will be an array off string of size=2*SmallAns
        int i = 0;
        for (; i < SmallAns.length; i++) {
            ans[i] = SmallAns[i]; //Copying all the strings present in SmallAns to ans string array
        }
        for (int k = 0; k < SmallAns.length; k++) {
            ans[k + SmallAns.length] = givenString.charAt(0) + SmallAns[k]; // Insert character at index=0 of the given substring in front of every string in SmallAns
        }
        return ans;
    }
}