[leetcode]216. Combination Sum III
Analysis
电脑坏了—— [心塞!!]
Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.
Note:
All numbers will be positive integers.
The solution set must not contain duplicate combinations.
递归解决~
Implement
class Solution {
public:
vector<vector<int>> combinationSum3(int k, int n) {
vector<int> tmp;
helper(k, n, 1, tmp);
return res;
}
void helper(int k, int n, int l, vector<int>& tmp){
if(n < 0)
return ;
if(n == 0 && tmp.size() == k)
res.push_back(tmp);
for(int i=l; i<=9; i++){
tmp.push_back(i);
helper(k, n-i, i+1, tmp);
tmp.pop_back();
}
}
private:
vector<vector<int>> res;
};