【LeetCode热题100】【回溯】子集

class Solution {
public:
    vector<vector<int> > ans;

    vector<vector<int> > subsets(vector<int> &nums) {
        int n = nums.size();
        for (int binary = 0; binary < 1 << n; ++binary) {
            vector<int> son;
            for (int i = 0; i < n; i++) {
                if (binary >> i & i)
                    son.push_back(nums[i]);
            }
            ans.push_back(std::move(son));
        }
        return ans;
    }
};

class Solution {
public:
    vector<vector<int> > ans;
    vector<int> nums;
    vector<int> array;

    void dfs(int depth) {
        if (depth == nums.size()) {
            ans.push_back(array);
            return;
        }
        array.push_back(nums[depth]);
        dfs(depth + 1);
        array.pop_back();
        dfs(depth + 1);
    }

    vector<vector<int> > subsets(vector<int> &nums) {
        this->nums = nums;
        dfs(0);
        return ans;
    }
};