46. Permutations

leetcode.com/problems/permutations/submissions/

Permutations - LeetCode

class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> ret = new ArrayList<>();
        List<Integer> tmp = new ArrayList();
        backtrack(nums, ret, tmp);
        return ret;
    }
    
    public void backtrack(int[] nums, List<List<Integer>> ret, List<Integer> tmp) {
        // base case
        if(tmp.size() == nums.length) {
            ret.add(new ArrayList<Integer>(tmp));
            return;
        }
        
        // recursion
        for(int num:nums) {
            if(tmp.contains(num)) continue;
            tmp.add(num);
            backtrack(nums, ret, tmp);
            tmp.remove(tmp.size()-1);
        }
    }
}