46. Permutations

backtrack

 

 

 

class Solution {
    List<List<Integer>> res = new ArrayList<>();
    public List<List<Integer>> permute(int[] nums) {
        backtrack(nums, new ArrayList<>());
        return res;
    }
    
    public void backtrack(int[] nums, List<Integer> list) {
        if(list.size() == nums.length) {
            res.add(new ArrayList<>(list));
        }
        for(int i = 0; i < nums.length; i++) {
            if(list.contains(nums[i])) continue;
            list.add(nums[i]);
            backtrack(nums, list);
            list.remove(list.size() - 1);
        }
    }   
}