subsets template

模板1， dfs 不带循环

class Solution {
public:
    /**
     * @param nums: A set of numbers
     * @return: A list of lists
     */
    vector<vector<int>> subsets(vector<int> &nums) {
        vector<vector<int>> ans;
        vector<int> path;
        sort(nums.begin(), nums.end());
        dfs(ans, path, 0, nums);
        return ans;
    }
    void dfs(vector<vector<int>>& ans, vector<int>& path, int index, vector<int>& nums) {
        if (index == nums.size()) {
            ans.push_back(path);
            return;
        }
        path.push_back(nums[index]);
        dfs(ans, path, index+1, nums);
        path.pop_back();
        dfs(ans, path, index+1, nums);
    }
};

模板2， dfs 带循环

class Solution {
public:
    /**
     * @param nums: A set of numbers
     * @return: A list of lists
     */
    vector<vector<int>> subsets(vector<int> &nums) {
        vector<vector<int>> ans;
        vector<int> path;
        sort(nums.begin(), nums.end());
        dfs(ans, path, 0, nums);
        return ans;
    }
    void dfs(vector<vector<int>>& ans, vector<int>& path, int index, vector<int>& nums) {
        ans.push_back(path);
        for (int i = index; i < nums.size(); ++i) {
            path.push_back(nums[i]);
            dfs(ans, path, i+1, nums);
            path.pop_back();
        }
    }
};