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);
}
}
}

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