This articles shows few ways of writing a java program for finding all permutations of characters in a string.
 

This article only focusses only on the recursive approaches.
 
 

Java programs for string permutations using recursion :

 

Program 1 : Heap’s algorithm

package com.topjavatutorial;

import java.util.Arrays;
import java.util.Scanner;

public class ExampleAllPermutationOfString {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    
    System.out.println("Enter a String : ");
    
    String str = sc.next();
    
    generate(str.toCharArray(),str.length());
  }

    public static void generate(char[] arr, int n) {
        if (n == 1) {
            System.out.println(Arrays.toString(arr));
        } else {
            for (int i = 0; i < n-1; i++) {
              generate(arr, n - 1);

                // odd or even
                if (n % 2 == 1) {
                    swap(arr, 0, n - 1);
                } else {
                    swap(arr, i, n - 1);
                }
            }
            generate(arr, n - 1);
        }
    }
    
  private static void swap(char[] arr, int right, int left) {
        char temp = arr[right];
        arr[right] = arr[left];
        arr[left] = temp;
    }
}

 
 

Output

Enter a String :
abc
[a, b, c]
[b, a, c]
[c, a, b]
[a, c, b]
[b, c, a]
[c, b, a]

 
 

Program 2

package com.topjavatutorial;

import java.util.Scanner;

public class ExampleAllPermutationOfString {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    
    System.out.println("Enter a String : ");
    
    String str = sc.next();
    
    permutation(str);
  }
  
  public static void permutation(String str) { 
      permutation("", str); 
  }

  private static void permutation(String prefix, String str) {
      int n = str.length();
      if (n == 0) System.out.println(prefix);
      else {
          for (int i = 0; i < n; i++)
              permutation(prefix + str.charAt(i), str.substring(0, i) + str.substring(i+1, n));
      }
  }

}

 
 

Output

Enter a String :
abc
abc
acb
bac
bca
cab
cba

 

Reference

 
https://en.wikipedia.org/wiki/Heap%27s_algorithm
http://introcs.cs.princeton.edu/java/23recursion/Permutations.java.html

 
 

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