package Recursion;

import java.util.*;

import java.util.stream.Collectors;

public class Permutations {

/*

Given aan array of integers, generate its permutations

eg : <2,3,5,7>

<2,3,7,5> , <2,5,3,7>, <5,3,2,7> and so on.

*/

public static List<List<Integer>> generatePermutations(List<Integer> inputList) {

List<List<Integer>> result = new ArrayList<>();

directedPermutations(0, inputList, result);

return result;

}

private static void directedPermutations(int i, List<Integer> inputList,

List<List<Integer>> result) {

if (i == inputList.size() - 1) {

result.add(new ArrayList<>(inputList));

return;

}

// Try every possibility for A[i].

for (int j = i; j < inputList.size(); ++j) {

//use the same inputList swap the numbers.

Collections.swap(inputList, i, j);

// Generate all permutations for A.subList(i + 1, A.size()).

directedPermutations(i + 1, inputList, result);

Collections.swap(inputList, i, j);

}

}

public static void main(String[] args) {

List <Integer> input = new ArrayList<>();

input.add(2);

input.add(3);

input.add(5);

List<List<Integer>> result = generatePermutations(input);

for(List<Integer> l : result){

System.out.print("<");

for (int i : l){

System.out.print(i+",");

}

System.out.print("> ,");

}

}

}