LeetCode *** 39. Combination Sum

题目：

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in
C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

All numbers (including target) will be positive integers.
Elements in a combination (a1,
a2, … , ak) must be in non-descending order. (ie,
a1 ≤ a2 ≤ … ≤
ak).
The solution set must not contain duplicate combinations.

For example, given candidate set

2,3,6,7

and target

7

,

A solution set is:

[7]

[2, 2, 3]

分析：

睡了一觉感觉自己精神都好很多。。

代码：

class Solution {
public:
int tg;
vector<vector<int>> res;
vector<vector<int>> combinationSum(vector<int>& candidates, int target) {

sort(candidates.begin(),candidates.end());
tg=target;
vector<int>tmp;
dfs(candidates,tmp,0,0);
return res;

}

void dfs(vector<int>& nums,vector<int> tmp,int start,int sum){
int s;
for(int i=start;i<nums.size();i++){
s=sum+nums[i];
if(s<tg){
tmp.push_back(nums[i]);
dfs(nums,tmp,i,s);
tmp.erase(tmp.end()-1);
}else if(s==tg){
tmp.push_back(nums[i]);
res.push_back(tmp);
tmp.erase(tmp.end()-1);
}
}

}
};