Merge pull request TheAlgorithms#120 from nimit17/ReturnSubsequences

Algorithm to Return Subsequences

Author: dynamitechetan

Misc/ReturnSubsequence.java

@@ -0,0 +1,59 @@
+/*
+This program will return all the subsequences of the input string in a string array;
+Sample Input:
+abc
+Sample Output:
+"" ( Empty String )
+c
+b
+bc
+a
+ac
+ab
+abc
+
+ */
+
+import java.util.Scanner;
+
+public class ReturnSubsequence {
+    /*
+    Main function will accept the given string and implement return subsequences function
+     */
+    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 : ");
+        for(int i=0;i<subsequence.length;i++) //print the given array of subsequences
+        {
+            System.out.println(subsequence[i]);
+        }
+    }
+     /*
+     Recursive function to return Subsequences
+      */
+    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;
+    }
+}