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package medium;

import java.util.ArrayList;

import java.util.List;

public class Permutations46 {

public static List<List<Integer>> permute1(int[] nums) {

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

ArrayList<Integer> templist = new ArrayList<>();

permute1(nums, templist, list);

return list;

}

private static void permute1(int[] nums, List<Integer> temp, List<List<Integer>> list) {

if (temp.size() == nums.length) {

list.add(new ArrayList<>(temp));

return;

}

for (int i = 0; i < nums.length; i++) {

if (temp.contains(nums[i]))

continue;

temp.add(nums[i]);

permute1(nums, temp, list);

temp.remove(temp.size() - 1);

}

}

// O(N!) Time - using visited mark

public static List<List<Integer>> permute(int[] nums) {

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

boolean[] visited = new boolean[nums.length];

backtrack(nums, visited, new ArrayList<Integer>(), result);

return result;

}

private static void backtrack(int[] nums, boolean[] visited, ArrayList<Integer> permutations,

List<List<Integer>> result) {

if (permutations.size() == nums.length) {

result.add(new ArrayList<>(permutations)); // deep-copy

return;

}

for (int i = 0; i < nums.length; i++) {

if (visited[i] == true)

continue;

permutations.add(nums[i]);

visited[i] = true;

backtrack(nums, visited, permutations, result);

permutations.remove(permutations.size() - 1); // remove recently

// visited

visited[i] = false;

}

}

public static void main(String[] args) {

int[] nums = { 1, 2, 3 };

System.out.println(permute(nums));

}

}