JavaAlgorithms/Others/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;
  }
}