Java Program to Generate All Subsets of a Given Set in the Gray Code Order

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This is a java program to generate and print all the subsets using the Gray Code Order. The reflected binary code, also known as Gray code after Frank Gray, is a binary numeral system where two successive values differ in only one bit (binary digit). The gray code equivalent of a binary number is (number >> 1) ^ number, i.e. right-shift the number by one and EX-ORing with the original number.

Here is the source code of the Java Program to Generate All Subsets of a Given Set in the Gray Code Order. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

  1. //This is a java program to generate all subsets of given set of numbers using gray code order
  2. import java.util.Random;
  3. import java.util.Scanner;
  4.  
  5. public class Gray_Code_Permutation 
  6. {
  7.     public static int[] grayCode(int N) 
  8.     {
  9.         int[] grayCode = new int[(int) Math.pow(2, N)];
  10.         int[] binary = new int[(int) Math.pow(2, N)];
  11.  
  12.         for (int i = 0; i < Math.pow(2, N); i++)
  13.             grayCode[i] = (i >> 1) ^ i;
  14.  
  15.         for (int i = 0; i < Math.pow(2, N); i++) 
  16.         {
  17.             int b = 1;
  18.             binary[i] = 0;
  19.             while (grayCode[i] > 0) 
  20.             {
  21.                 binary[i] += (grayCode[i] % 2) * b;
  22.                 grayCode[i] /= 2;
  23.                 b = b * 10;
  24.             }
  25.         }
  26.         return binary;
  27.     }
  28.  
  29.     public static void main(String args[]) 
  30.     {
  31.         Random random = new Random();
  32.         Scanner sc = new Scanner(System.in);
  33.         System.out.println("Enter the number of elements in the set: ");
  34.         int N = sc.nextInt();
  35.         int[] sequence = new int[N];
  36.         for (int i = 0; i < N; i++)
  37.             sequence[i] = Math.abs(random.nextInt(100));
  38.  
  39.         System.out.println("The elements in the set : ");
  40.         for (int i = 0; i < N; i++)
  41.             System.out.print(sequence[i] + " ");
  42.  
  43.         int[] mask = new int[(int) Math.pow(2, N)];
  44.         mask = grayCode(N);
  45.  
  46.         System.out.println("\nThe permutations are: ");
  47.         for (int i = 0; i < Math.pow(2, N); i++) 
  48.         {
  49.             System.out.print("{ ");
  50.             for (int j = 0; j < N; j++) 
  51.             {
  52.                 if (mask[i] % 10 == 1)
  53.                     System.out.print(sequence[j] + " ");
  54.                 mask[i] /= 10;
  55.             }
  56.             System.out.println("}");
  57.         }
  58.         sc.close();
  59.     }
  60. }

Output:

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$ javac Gray_Code_Permutation.java
$ java Gray_Code_Permutation
 
Enter the number of elements in the set: 
4
The elements in the set : 
36 75 15 59 
The permutations are: 
{ }
{ 36 }
{ 36 75 }
{ 75 }
{ 75 15 }
{ 36 75 15 }
{ 36 15 }
{ 15 }
{ 15 59 }
{ 36 15 59 }
{ 36 75 15 59 }
{ 75 15 59 }
{ 75 59 }
{ 36 75 59 }
{ 36 59 }
{ 59 }
 
Enter the number of elements in the set: 
3
The elements in the set : 
73 36 36 
The permutations are: 
{ }
{ 73 }
{ 73 36 }
{ 36 }
{ 36 36 }
{ 73 36 36 }
{ 73 36 }
{ 36 }

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter