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.
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]]
Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.
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思路：
与【Combinations】类似，稍作修改即可。
c++ code:
class Solution {
public:
vector<vector<int>> combinationSum3(int k, int n) {
vector<vector<int>> combs;
vector<int> comb;
combine(combs,comb,1,k,n);
return combs;
}
// 自定义函数
void combine(vector<vector<int>> &combs, vector<int> &comb,int begin,int k, int n) {
if(k==0 && n==0) {
// vector<int> t(comb);
combs.push_back(comb);
return;
}
for(int i=begin;i<=9;i++) {
comb.push_back(i);
combine(combs,comb,i+1,k-1,n-i);
comb.pop_back();
}
}
};原文：http://blog.csdn.net/itismelzp/article/details/51623003