Java Program to Implement Heap’s Algorithm for Generating Permutations

This is a java program to find permutation of N numbers using Heap’s Algorithm. Heap’s algorithm is an algorithm used for generating all possible permutations of some given length.

Here is the source code of the Java Program to Implement Heap’s Algorithm for Permutation of N Numbers. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

  1.  
  2. package com.sanfoundry.combinatorial;
  3.  
  4. import java.util.Arrays;
  5. import java.util.Scanner;
  6.  
  7. public class HeapsPermutation
  8. {
  9.     private static void swap(int[] v, int i, int j)
  10.     {
  11.         int t = v[i];
  12.         v[i] = v[j];
  13.         v[j] = t;
  14.     }
  15.  
  16.     public void permute(int[] v, int n)
  17.     {
  18.         if (n == 1)
  19.         {
  20.             System.out.println(Arrays.toString(v));
  21.         }
  22.         else
  23.         {
  24.             for (int i = 0; i < n; i++)
  25.             {
  26.                 permute(v, n - 1);
  27.                 if (n % 2 == 1)
  28.                 {
  29.                     swap(v, 0, n - 1);
  30.                 }
  31.                 else
  32.                 {
  33.                     swap(v, i, n - 1);
  34.                 }
  35.             }
  36.         }
  37.     }
  38.  
  39.     public static void main(String[] args)
  40.     {
  41.         System.out.println("Enter the number of elements in a sequence: ");
  42.         Scanner sc = new Scanner(System.in);
  43.         int n = sc.nextInt();
  44.         System.out.println("Enter the sequence: ");
  45.         int sequence[] = new int[n];
  46.         for (int i = 0; i < n; i++)
  47.         {
  48.             sequence[i] = sc.nextInt();
  49.         }
  50.         new HeapsPermutation().permute(sequence, n);
  51.         sc.close();
  52.     }
  53. }

Output:

$ javac HeapsPermutation.java
$ java HeapsPermutation
 
Enter the number of elements in a sequence: 
5
Enter the sequence: 
2 4 7 3 8
[2, 4, 7, 3, 8]
[4, 2, 7, 3, 8]
[7, 2, 4, 3, 8]
[2, 7, 4, 3, 8]
[4, 7, 2, 3, 8]
[7, 4, 2, 3, 8]
[3, 4, 7, 2, 8]
[4, 3, 7, 2, 8]
[7, 3, 4, 2, 8]
[3, 7, 4, 2, 8]
[4, 7, 3, 2, 8]
[7, 4, 3, 2, 8]
[3, 2, 7, 4, 8]
[2, 3, 7, 4, 8]
[7, 3, 2, 4, 8]
[3, 7, 2, 4, 8]
[2, 7, 3, 4, 8]
[7, 2, 3, 4, 8]
[3, 2, 4, 7, 8]
[2, 3, 4, 7, 8]
[4, 3, 2, 7, 8]
[3, 4, 2, 7, 8]
[2, 4, 3, 7, 8]
[4, 2, 3, 7, 8]
[8, 2, 4, 7, 3]
[2, 8, 4, 7, 3]
[4, 8, 2, 7, 3]
[8, 4, 2, 7, 3]
[2, 4, 8, 7, 3]
[4, 2, 8, 7, 3]
[7, 2, 4, 8, 3]
[2, 7, 4, 8, 3]
[4, 7, 2, 8, 3]
[7, 4, 2, 8, 3]
[2, 4, 7, 8, 3]
[4, 2, 7, 8, 3]
[7, 8, 4, 2, 3]
[8, 7, 4, 2, 3]
[4, 7, 8, 2, 3]
[7, 4, 8, 2, 3]
[8, 4, 7, 2, 3]
[4, 8, 7, 2, 3]
[7, 8, 2, 4, 3]
[8, 7, 2, 4, 3]
[2, 7, 8, 4, 3]
[7, 2, 8, 4, 3]
[8, 2, 7, 4, 3]
[2, 8, 7, 4, 3]
[3, 8, 2, 4, 7]
[8, 3, 2, 4, 7]
[2, 3, 8, 4, 7]
[3, 2, 8, 4, 7]
[8, 2, 3, 4, 7]
[2, 8, 3, 4, 7]
[4, 8, 2, 3, 7]
[8, 4, 2, 3, 7]
[2, 4, 8, 3, 7]
[4, 2, 8, 3, 7]
[8, 2, 4, 3, 7]
[2, 8, 4, 3, 7]
[4, 3, 2, 8, 7]
[3, 4, 2, 8, 7]
[2, 4, 3, 8, 7]
[4, 2, 3, 8, 7]
[3, 2, 4, 8, 7]
[2, 3, 4, 8, 7]
[4, 3, 8, 2, 7]
[3, 4, 8, 2, 7]
[8, 4, 3, 2, 7]
[4, 8, 3, 2, 7]
[3, 8, 4, 2, 7]
[8, 3, 4, 2, 7]
[7, 3, 8, 2, 4]
[3, 7, 8, 2, 4]
[8, 7, 3, 2, 4]
[7, 8, 3, 2, 4]
[3, 8, 7, 2, 4]
[8, 3, 7, 2, 4]
[2, 3, 8, 7, 4]
[3, 2, 8, 7, 4]
[8, 2, 3, 7, 4]
[2, 8, 3, 7, 4]
[3, 8, 2, 7, 4]
[8, 3, 2, 7, 4]
[2, 7, 8, 3, 4]
[7, 2, 8, 3, 4]
[8, 2, 7, 3, 4]
[2, 8, 7, 3, 4]
[7, 8, 2, 3, 4]
[8, 7, 2, 3, 4]
[2, 7, 3, 8, 4]
[7, 2, 3, 8, 4]
[3, 2, 7, 8, 4]
[2, 3, 7, 8, 4]
[7, 3, 2, 8, 4]
[3, 7, 2, 8, 4]
[4, 7, 3, 8, 2]
[7, 4, 3, 8, 2]
[3, 4, 7, 8, 2]
[4, 3, 7, 8, 2]
[7, 3, 4, 8, 2]
[3, 7, 4, 8, 2]
[8, 7, 3, 4, 2]
[7, 8, 3, 4, 2]
[3, 8, 7, 4, 2]
[8, 3, 7, 4, 2]
[7, 3, 8, 4, 2]
[3, 7, 8, 4, 2]
[8, 4, 3, 7, 2]
[4, 8, 3, 7, 2]
[3, 8, 4, 7, 2]
[8, 3, 4, 7, 2]
[4, 3, 8, 7, 2]
[3, 4, 8, 7, 2]
[8, 4, 7, 3, 2]
[4, 8, 7, 3, 2]
[7, 8, 4, 3, 2]
[8, 7, 4, 3, 2]
[4, 7, 8, 3, 2]
[7, 4, 8, 3, 2]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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