1877-minimize-maximum-pair-sum-in-array.rb

# frozen_string_literal: true

# 1877. Minimize Maximum Pair Sum in Array
# Medium
# https://leetcode.com/problems/minimize-maximum-pair-sum-in-array

=begin
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.

Example 1:
Input: nums = [3,5,2,3]
Output: 7
Explanation: 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: 8
Explanation: 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.

Constraints:
n == nums.length
2 <= n <= 105
n is even.
1 <= nums[i] <= 105
=end

# @param {Integer[]} nums
# @return {Integer}
def min_pair_sum(nums)
  nums.sort!.reverse.zip(nums).map(&:sum).max
end

# **************** #
#       TEST       #
# **************** #

require "test/unit"
class Test_min_pair_sum < Test::Unit::TestCase
  def test_
    assert_equal 7, min_pair_sum([3, 5, 2, 3])
    assert_equal 8, min_pair_sum([3, 5, 4, 2, 4, 6])
  end
end