Given a set of distinct integers, nums, return all possible subsets (the power set).

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],
  []
]

題意：給你一個(gè)集合，求所有的子集

思路：深搜

代碼:

class Solution {
    public List<List<Integer>> subsets(int[] nums) {  
        List<List<Integer>> res = new ArrayList<List<Integer>>();  
        List<Integer> temp = new ArrayList<Integer>();  
        dfs(res, temp, nums, 0);  
        return res;  
    }  
    private void dfs(List<List<Integer>> res, List<Integer> temp, int[] nums, int j) {  
        res.add(new ArrayList<Integer>(temp));  
        for(int i = j; i < nums.length; i++) {  
            temp.add(nums[i]);  //① 加入 nums[i]  
            dfs(res, temp, nums, i + 1);  //② 遞歸  
            temp.remove(temp.size() - 1);  //③ 移除 nums[i]  
        }  
    }  

}