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Java - Permutation Programs

Write a program that produces random permutations of the numbers 1 to 10. To generate a random permutation, you need to fill an array with the numbers 1 to 10 so that no two entries of the array have the same contents. You could do it by brute force, by calling Random.nextInt until it produces a value that is not yet in the array. Instead, you should implement a smart method. Make a second array and fill it with the numbers 1 to 10. Then pick one of those at random, remove it, and append it to the permutation array. Repeat 10 times. Implement a class PermutationGenerator with a method

int[] nextPermutation

Use the following class as your main class:

/**
This class prints 5 permutations of the numbers 1 through 10.
*/
public class PermutationPrinter
{
public static void main(String[] args)
{
PermutationGenerator gen = new PermutationGenerator(10);

for (int i = 1; i <= 5; i++)
{
for (int n : gen.nextPermutation())
System.out.print(" " + n);
System.out.println();
}
}
}

Complete the following class in your solution:

import java.util.Random;

/**
This class generates permutations of a sequence of integers
1...length.
*/
public class PermutationGenerator
{
. . .

/**
Construct a PermutationGenerator object.
@param length the length of the permutations generated
by this generator.
*/
public PermutationGenerator(int length)
{
. . .
}

/**
Gets the next permutation.
@return the array containing the next permutation
*/
public int[] nextPermutation()
{
. . .
}
}

Solution Summary

Java permutation programs are examined.

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