1464-maximum-product-of-two-elements-in-an-array.rb

# frozen_string_literal: true

# 1464. Maximum Product of Two Elements in an Array
# Easy
# https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array

=begin
Given the array of integers nums, you will choose two different indices i and j of that array. Return the maximum value of (nums[i]-1)*(nums[j]-1).

Example 1:
Input: nums = [3,4,5,2]
Output: 12
Explanation: If you choose the indices i=1 and j=2 (indexed from 0), you will get the maximum value, that is, (nums[1]-1)*(nums[2]-1) = (4-1)*(5-1) = 3*4 = 12.

Example 2:
Input: nums = [1,5,4,5]
Output: 16
Explanation: Choosing the indices i=1 and j=3 (indexed from 0), you will get the maximum value of (5-1)*(5-1) = 16.

Example 3:
Input: nums = [3,7]
Output: 12

Constraints:
2 <= nums.length <= 500
1 <= nums[i] <= 10^3
=end

# @param {Integer[]} nums
# @return {Integer}
def max_product(nums)
  vice = max = 0
  nums.each do |num|
    next if num < vice
    vice, max = [num, max].minmax
  end
  (vice - 1) * (max - 1)
end

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

require "test/unit"
class Test_max_product < Test::Unit::TestCase
  def test_
    assert_equal 12, max_product([3, 4, 5, 2])
    assert_equal 16, max_product([1, 5, 4, 5])
    assert_equal 12, max_product([3, 7])
  end
end