You are given two integers,?n?and?k.

An array of?distinct?positive integers is called a?k-avoiding?array if there does not exist any pair of distinct elements that sum to?k.

Return?the?minimum?possible sum of a k-avoiding array of length?n.

?

Example 1:

Input: n = 5, k = 4

Output: 18

Explanation: Consider the k-avoiding array [1,2,4,5,6], which has a sum of 18. It can be proven that there is no k-avoiding array with a sum less than 18.

Example 2:

Input: n = 2, k = 6

Output: 3

Explanation: We can construct the array [1,2], which has a sum of 3. It can be proven that there is no k-avoiding array with a sum less than 3.

?

Constraints:

• 1 <= n, k <= 50

數(shù)字都比較小，直接累加遍歷即可，只是要保留一個(gè)集合，用于判斷是否有差值在集合中即可；

下面是代碼：

Runtime:?7 ms, faster than?100.00%?of?Java?online submissions for?Determine the Minimum Sum of a k-avoiding Array.

Memory Usage:?43.5 MB, less than?100.00%?of?Java?online submissions for?Determine the Minimum Sum of a k-avoiding Array.