Permutations of list of numbers

Given a collection of numbers, return all possible permutations.

Problem description:

Input:
list of numbers: [8, 4, 13]

Output:
all permutations of the numbers in the list

[8, 4, 13]

[4, 8, 13]

[4, 13, 8]

[8, 13, 4]

[13, 8, 4]

[13, 4, 8]

Solution 1:

/**
* do it iteratively
*/

public static ArrayList<ArrayList<Integer>> getPermutations(int[] nums){
ArrayList<ArrayList<Integer>> result = new ArrayList<>();

  //start with an empty list
  result.add(new ArrayList<Integer>());
 
  for(int i=0; i<nums.length; i++){
ArrayList<ArrayList<Integer>> temp = new ArrayList<>();

//go through the list from previous round and add the number into the list
   for(ArrayList<Integer> each : result){
for(int index = 0; index<=each.size(); index++){
ArrayList<Integer> dest = new ArrayList<>(each); //make a copy of original list
dest.add(index, nums[i]); //insert the number into all possible positions
temp.add(dest);
}
}
  
// switch over to prepare for the next round
 result = temp;
}
return result;
}

Solution 2:

/**

 *  do it recursively

**/

public static List<List<Integer>> getPermutations(List<Integer> nums){

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

if(nums.size()==0){

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

return result;

}

Integer n = nums.remove(0);

List<List<Integer>> subResult = getPermutations(nums); //get the permutation for sub list

for(List<Integer> each : subResult){

for(int index = 0; index<=each.size(); index++){

ArrayList<Integer> dest = new ArrayList<>(each); //make a copy of original list

dest.add(index, n); //insert the number into all possible positions

result.add(dest);

}

}

return result;

}