LeetCode: Combination Sum

第一次没考虑到要加个系数cur， 因为必须从小到大排序，导致答案里有[1, 2]和[2, 1]，加入cur后就acm了

class Solution {
public:
    void dfs(vector<int> candidates, int target, int sum, vector<int> &save, vector<vector<int>> &ret, int cur) {
        if (sum > target) return;
        if (sum == target) {
            ret.push_back(save);
            return;
        }
        for (int i = cur; i < candidates.size(); i++) {
            save.push_back(candidates[i]);
            dfs(candidates, target, sum+candidates[i], save, ret, i);
            save.pop_back();
        }
    }
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        sort(candidates.begin(), candidates.end());
        int sum = 0;
        vector<vector<int>> ret;
        vector<int> save;
        if (candidates.size() == 0) return ret;
        int cur = 0;
        dfs(candidates, target, sum, save, ret, cur);
        return ret;
    }
};

 C#: C#有深浅拷贝的问题，这里浅拷贝的话最后的ans就一直是空。。。所以这里需要深拷贝出来。。。C++没有这个问题方便很多

public class Solution {
    public List<List<int>> CombinationSum(int[] candidates, int target) {
        Array.Sort(candidates);
        int sum = 0;
        List<List<int>> ans = new List<List<int>>();
        List<int> tmp = new List<int>();
        if (candidates.Length == 0) return ans;
        int dep = 0;
        dfs(candidates, target, sum, ref tmp, ref ans, dep);
        return ans;
    }
    void dfs(int[] candidates, int target, int sum, ref List<int> tmp, ref List<List<int>> ans, int dep)
    {
        if (sum > target) return;
        if (sum == target) {
            List<int> newTmp = new List<int>();
            for (int i = 0; i < tmp.Count; i++) newTmp.Add(tmp[i]);
            ans.Add(newTmp);
            return;
        }
        for (int i = dep; i < candidates.Length; i++) {
            tmp.Add(candidates[i]);
            dfs(candidates, target, sum + candidates[i], ref tmp, ref ans, i);
            tmp.RemoveAt(tmp.Count - 1);
        }
    }
}