leetcode78

class Solution {
public:    
    int x[10000];
    vector<vector<int>> R;    
    
    int n;
    //t当前查询的位置
    void BackTrack(vector<int> nums, int t)
    {        
        if (t >= n)//达到叶子节点
        {
            vector<int> V;
            for (int i = 0; i < n; i++)
            {
                if (x[i] == 1)
                {
                    V.push_back(nums[i]);
                }                
            }        
            R.push_back(V);
            return;
        }
        x[t] = 0;
        BackTrack(nums, t + 1);

        x[t] = 1;
        BackTrack(nums, t + 1);        
    }

    vector<vector<int>> subsets(vector<int>& nums) {
        n = nums.size();
        memset(x, 0, sizeof(x));
        BackTrack(nums, 0);
        return R;
    }
};