package src;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class _46_Permute1 {
    List<List<Integer>> result = new ArrayList<>();
    LinkedList<Integer> path = new LinkedList<>();
    boolean[] used;

    public List<List<Integer>> permute(int[] nums) {
        if (nums.length == 0){
            return result;
        }
        used = new boolean[nums.length];
        permuteHelper(nums);
        return result;
    }

    private void permuteHelper(int[] nums){
        if (path.size() == nums.length){
            result.add(new ArrayList<>(path));
            return;
        }

        for (int i = 0; i < nums.length; i++){
            if (used[i]){
                continue;
            }

            used[i] = true;
            path.add(nums[i]);
            permuteHelper(nums);
            path.removeLast();
            used[i] = false;
        }
    }

    public static void main(String[] args) {
        int[] nums = new int[]{1, 2, 3};
        new _46_Permute1().permute(nums);
    }
}