CODE EXAMPLE FOR JAVA

Permutations of array in java

 
package org.arpit.java2blog;
 
import java.util.ArrayList;
import java.util.List;
 
public class PermutateArray {
 
    public static void main(String[] args) {
        PermutateArray pa=new PermutateArray();
 
        int[] arr= {10, 20, 30};
 
        List<List<Integer>> permute = pa.permute(arr);
 
        System.out.println("Permuations of array : [10, 20, 30] are:");
        System.out.println("=========================================");
        for(List<Integer> perm:permute)
        {
            System.out.println(perm);
        }
 
    }
    public List<List<Integer>> permute(int[] arr) {
        List<List<Integer>> list = new ArrayList<>();
        permuteHelper(list, new ArrayList<>(), arr);
        return list;
    }
 
    private void permuteHelper(List<List<Integer>> list, List<Integer> resultList, int [] arr){
 
        // Base case
        if(resultList.size() == arr.length){
            list.add(new ArrayList<>(resultList));
        }
        else{
            for(int i = 0; i < arr.length; i++){
 
                if(resultList.contains(arr[i]))
                {
                    // If element already exists in the list then skip
                    continue;
                }
                // Choose element
                resultList.add(arr[i]);
                // Explore
                permuteHelper(list, resultList, arr);
                // Unchoose element
                resultList.remove(resultList.size() - 1);
            }
        }
    }
 
}