题目链接:https://leetcode.com/problems/combination-sum-iii/
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]]
class Solution{
public:
vector<vector<int>> combinationSum3(int k,int n)
{
vector<vector<int>> result;
vector<int> com;
get(result,com,k,n,0,1);
return result;
}
void get(vector<vector<int>> &result,vector<int> com,int k,int n,int sum,int start)
{
if(k==0 && sum==n)
{
result.push_back(com);
return;
}
else if(k==0 && sum!=n)
{
return;
}
for(int i=start;i<=9;i++)
{
com.push_back(i);
get(result,com,k-1,n,sum+i,i+1);
com.pop_back();
}
}
};