- Combination Sum III
中等
https://leetcode.cn/problems/combination-sum-iii/
Find all valid combinations of k numbers that sum up to n such that the following conditions are true:
Only numbers 1 through 9 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.
Example 1:
Input: k = 3, n = 7
Output: [[1,2,4]]
Explanation:
1 + 2 + 4 = 7
There are no other valid combinations.
Example 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.
Example 3:
Input: k = 4, n = 1
Output: []
Explanation: There are no valid combinations.
Using 4 different numbers in the range [1,9], the smallest sum we can get is 1+2+3+4 = 10 and since 10 > 1, there are no valid combination.
Constraints:
2 <= k <= 9
1 <= n <= 60
相关企业
- 亚马逊 Amazon|3
- 谷歌 Google|3
- Facebook|2
相关标签
- Array
- Backtracking
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- Combination Sum 中等
class Solution:
def combinationSum3(self, k: int, n: int) -> List[List[int]]:
if n < 0:
return []
nums = [i for i in range(1, 10)]
results = []
self.dfs(nums, 0, [], k, n, results)
return results
def dfs(self, nums, currIndex, currSubset, k, target, resutls):
if len(currSubset) == k and sum(currSubset) == target:
resutls.append(list(currSubset))
for i in range(currIndex, len(nums)):
currSubset.append(nums[i])
self.dfs(nums, i+1, currSubset, k, target, resutls)
currSubset.pop()