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Maximum Product Difference Between Two Pairs

Problem statement​

The product difference between two pairs (a, b) and (c, d) is defined as (a * b) - (c * d).

  • For example, the product difference between (5, 6) and (2, 7) is (5 * 6) - (2 * 7) = 16.

Given an integer array nums, choose four distinct indices w, x, y, and z such that the product difference between pairs (nums[w], nums[x]) and (nums[y], nums[z]) is maximized.

Return the maximum such product difference.

Example 1:

Input: nums = [5,6,2,7,4]
Output: 34
Explanation: We can choose indices 1 and 3 for the first pair (6, 7) and indices 2 and 4 for the second pair (2, 4).
The product difference is (6 * 7) - (2 * 4) = 34.

Example 2:

Input: nums = [4,2,5,9,7,4,8]
Output: 64
Explanation: We can choose indices 3 and 6 for the first pair (9, 8) and indices 1 and 5 for the second pair (2, 4).
The product difference is (9 * 8) - (2 * 4) = 64.

Constraints:

  • 4 <= nums.length <= 104
  • 1 <= nums[i] <= 104

My solution​

/**
 * @param {number[]} nums
 * @return {number}
 */
var maxProductDifference = function(nums) {
    let min = Number.MAX_SAFE_INTEGER;
    let prevMin = min;
    let max = 0;
    let prevMax = max;
    
    for (const num of nums) {
        if (num > max) {
            prevMax = max;
            max = num
        } else if (num > prevMax) {
            prevMax = num
        }
        
        if (num < min) {            
            prevMin = min;
            min = num
        } else if (num < prevMin) {
            prevMin = num
        }
        // console.log(min, prevMin)
    }
    
    // console.log(max, prevMax, min, prevMin)
    
    return max * prevMax - min * prevMin
};