# 216. 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.

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]]
``````

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

``````class Solution {
public:
vector<vector<int> > combinationSum3(int k, int n) {
vector<vector<int> > res;
vector<int> out;
combinationSum3DFS(k, n, 1, out, res);
return res;
}
void combinationSum3DFS(int k, int n, int level, vector<int> &out, vector<vector<int> > &res) {
if (n < 0) return;
if (n == 0 && out.size() == k) res.push_back(out);
for (int i = level; i <= 9; ++i) {
out.push_back(i);
combinationSum3DFS(k, n - i, i + 1, out, res);
out.pop_back();
}
}
};
``````

Combination Sum II

Combination Sum

LeetCode All in One 题目讲解汇总(持续更新中…)

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