Leetcode#39 Combination Sum

原题地址

排序+DFS

与Combination Sum II（参见这篇文章）不同的地方在于，重复的数字可以使用多次，无所谓啦，反正代码几乎都一样。

代码：

vector<vector<int> > res;

void dfs(vector<int> &candidates, vector<int> ans, int pos, int left) {
  if (left == 0)
    res.push_back(ans);

  for (int i = pos; i < candidates.size() && candidates[i] <= left; i++)
    if (i == pos || candidates[i] > candidates[i - 1]) {
      ans.push_back(candidates[i]);
      dfs(candidates, ans, i, left - candidates[i]);
      ans.pop_back();
    }
}

vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
  sort(candidates.begin(), candidates.end());
  dfs(candidates, vector<int>(), 0, target);

  return res;
}