leetcode : subsets

Given a set of distinct integers, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

思路： 深度优先， 回溯剪枝    dfs   backtracking

public class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        
        List<List<Integer>> result = new ArrayList<List<Integer>>();
        if(nums == null || nums.length == 0){
            return result;
        }
        List<Integer> list = new ArrayList<Integer>();
        dfs(result, list, nums, 0);
        return result;
        
    }
    
    public void dfs(List<List<Integer>> result, List<Integer> list,int[] nums, int position){
        
        if(position > nums.length){
            return;
        }
        
        result.add(new ArrayList<Integer>(list));
        
        for(int i = position; i < nums.length; i++){
            list.add(nums[i]);
            dfs(result, list, nums, i + 1);
            list.remove(list.size() - 1);
        }
        
    }
    
    
}