Combination Sum III - LeetCode

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.

Ensure that numbers within the set are sorted in ascending order.

Example 1:

Input: k = 3, n = 7

Output:

[[1,2,4]]

Example 2:

Input: k = 3, n = 9

Output:

[[1,2,6], [1,3,5], [2,3,4]]

思路：这道题和Combination Sum II的思路类似。只不过candidates数组里只有1-9这9个数，且增加了累加次数的限制。

 class Solution {
 public:
     void assist(vector<vector<int> >& res, vector<int>& cur, int target, int k, int st)
     {
         if (k == )
         {
             if (target == )
                 res.push_back(cur);
             return;
         }
         for (int i = st; i <= ; i++)
         {
             cur.push_back(i);
             assist(res, cur, target - i, k - , i + );
             cur.pop_back();
         }
     }
     vector<vector<int>> combinationSum3(int k, int n) {
         vector<vector<int> > res;
         vector<int> cur;
         assist(res, cur, n, k, );
         return res;
     }
 };