Leetcode#40 Combination Sum II

排序+DFS
代码：
 1 vector<vector<int> > res;
 2     
 3 void dfs(vector<int> &num, vector<int> &ans, int pos, int left) {
 4   if (left == 0)
 5     res.push_back(ans);
 6   for (int i = pos; i < num.size() && num[i] <= left; i++) {
 7     if (i == pos || num[i] > num[i - 1]) {
 8       ans.push_back(num[i]);
 9       dfs(num, ans, i + 1, left - num[i]);
10       ans.pop_back();
11     }
12   }
13 }
14     
15 vector<vector<int> > combinationSum2(vector<int> &num, int target) {
16   sort(num.begin(), num.end());
17   vector<int> ans;
18   dfs(num, ans, 0, target);
19   return res;
20 }