The?pair sum?of a pair?(a,b)?is equal to?a + b. The?maximum pair sum?is the largest?pair sum?in a list of pairs.

• For example, if we have pairs?(1,5),?(2,3), and?(4,4), the?maximum pair sum?would be?max(1+5, 2+3, 4+4) = max(6, 5, 8) = 8.

Given an array?nums?of?even?length?n, pair up the elements of?nums?into?n / 2?pairs such that:

• Each element of?nums?is in?exactly one?pair, and

• The?maximum pair sum?is?minimized.

Return?the minimized?maximum pair sum?after optimally pairing up the elements.

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Example 1:

Input: nums = [3,5,2,3]Output: 7Explanation: The elements can be paired up into pairs (3,3) and (5,2). The maximum pair sum is max(3+3, 5+2) = max(6, 7) = 7.

Example 2:

Input: nums = [3,5,4,2,4,6]Output: 8Explanation: The elements can be paired up into pairs (3,5), (4,4), and (6,2). The maximum pair sum is max(3+5, 4+4, 6+2) = max(8, 8, 8) = 8.

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Constraints:

• n == nums.length

• 2 <= n <= 105

• n?is?even.

• 1 <= nums[i] <= 105

其實(shí)就是排序，最小的跟最大的配對，以此類推，然后這些配對中找最大的。

Runtime:?73 ms, faster than?42.32%?of?Java?online submissions for?Minimize Maximum Pair Sum in Array.

Memory Usage:?106.8 MB, less than?50.66%?of?Java?online submissions for?Minimize Maximum Pair Sum in Array.