标签：rom void each only put can out ++ add
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:
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：回溯法
1 class Solution { 2 public: 3 vector<vector<int>> combinationSum3(int k, int n) { 4 if (k <= 0) 5 return {}; 6 vector<vector<int> > res; 7 vector<int> v; 8 combinationSum3(k, n, res, v, 1); 9 return res; 10 } 11 private: 12 void combinationSum3(int k, int n, vector<vector<int> > &res, vector<int> &v, int begin) { 13 if (int(v.size()) == k && n == 0) { 14 res.push_back(v); 15 return ; 16 } 17 for (int i = begin; i <= 9 && n >= i; i++) { 18 v.push_back(i); 19 combinationSum3(k, n - i, res, v, i + 1); 20 v.pop_back(); 21 } 22 } 23 };
leetcode 216. Combination Sum III
标签：rom void each only put can out ++ add
原文地址：https://www.cnblogs.com/qinduanyinghua/p/11429723.html
