/*

46. Permutations

Medium

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

Input: nums = [1,2,3]

Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]

Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]

Output: [[1]]

Constraints:

1 <= nums.length <= 6

-10 <= nums[i] <= 10

All the integers of nums are unique.

*/

//CODE 1:

class Solution {

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

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

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

Solve(nums,subres,res);

return res;

}

public static void Solve(int nums[],List<Integer> subres,List<List<Integer>> res){

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

res.add(new ArrayList<Integer>(subres));

return;

}else{

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

if(subres.contains(nums[i])) continue;

subres.add(nums[i]);

Solve(nums,subres,res);

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

}

}

}

}

// CODE 2:

class Solution {

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

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

Solve(nums,0,res);

return res;

}

public static void Solve(int nums[],int idx,List<List<Integer>> res){

if(idx==nums.length){

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

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

nn.add(nums[i]);

}

res.add(new ArrayList<Integer>(nn));

return;

}else{

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

swap(i,idx,nums);

Solve(nums,idx+1,res);

swap(i,idx,nums);

}

}

}

public static void swap(int i,int j,int[] nums){

int temp = nums[i];

nums[i] = nums[j];

nums[j] = temp;

}

}