g0201_0300.s0216_combination_sum_iii

Class Solution

java.lang.Object

g0201_0300.s0216_combination_sum_iii.Solution

public class Solution
extends Object

216 - Combination Sum III.

Medium

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. 

Example 4:

Input: k = 3, n = 2

Output: []

Explanation: There are no valid combinations.

Example 5:

Input: k = 9, n = 45

Output: 1,2,3,4,5,6,7,8,9

Explanation:

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45
There are no other valid combinations. 

Constraints:

• 2 <= k <= 9
• 1 <= n <= 60

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
List<List<Integer>>	combinationSum3(int k, int n)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

combinationSum3

public List<List<Integer>> combinationSum3(int k,
                                           int n)