LeetCode 1464. Maximum Product of Two Elements in an Array

Description

https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/

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

Explanation

Find the first largest number and the second-largest number, then calculate the product.

Python Solution

class Solution:
    def maxProduct(self, nums: List[int]) -> int:
        
        max_num_index = -1     
        for i, num in enumerate(nums):
            if max_num_index == -1 or num > nums[max_num_index]:
                max_num_index = i
        

        second_num_index = -1                
        for i, num in enumerate(nums):
            if (i != max_num_index and (num > nums[second_num_index] or second_num_index == -1)):
                second_num_index = i


        return (nums[max_num_index] - 1) * (nums[second_num_index] - 1)
  • Time Complexity: ~N
  • Space Complexity: ~1

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