题目描述
Find all valid combinations of
k
numbers that sum up ton
such that the following conditions are true:
- Only numbers
1
through9
are used.- Each number is used at most once.
Return a list of all possible valid combinations. The list must not contain the same combination twice, and the combinations may be returned in any order.
例子
例子 1
Input:
k = 3, n = 7
Output:[[1,2,4]]
Explanation:
1 + 2 + 4 = 7
There are no other valid combinations.
例子 2
Input:
k = 3, n = 9
Output:[[1,2,6],[1,3,5],[2,3,4]]
Explanation:
1 + 2 + 6 = 9
1 + 3 + 5 = 9
2 + 3 + 4 = 9
There are no other valid combinations.
例子 3
Input:
k = 4, n = 1
Output:[]
Explanation: There are no valid combinations.[1,2,1]
is not valid because 1 is used twice.
Constraints
2 <= k <= 9
1 <= n <= 60
解题思路
参考 [Leetcode]40. Combination Sum II(C++), 思路大同小异,代码如下:
1 |
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- 时间复杂度: O(n!)
- 空间复杂度: O(n!)
GitHub 代码同步地址: 216.CombinationSumIii.cpp
其他题目:
GitHub: Leetcode-C++-Solution
博客: Leetcode-Solutions