LeetCode Subsets

题目：

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

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

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

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

class Solution {public:vector<vector<int> > subsets(vector<int> &S) {sort(S.begin(), S.end());int n = S.size();vector<int> row;ans.clear();dfs(0, row, n, S);return ans;}private:    vector<vector<int>> ans;    //每个元素有取和不取两种选择，使用深度搜索，共2^n(n为集合大小)个子集void dfs(int depth, vector<int> row, int n, vector<int> &S) {if (depth == n) {ans.push_back(row);return;}dfs(depth + 1, row, n, S);row.push_back(S[depth]);dfs(depth + 1, row, n, S);}};