QUESTION:

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 <= 10^4
1 <= nums[i] <= 10^4

EXPLANATION:

简单的题目, 贪心算法, 两个最大的相乘减去你个最小的相乘. 所以先排序一下就行.

SOLUTION:

class Solution {
    func maxProductDifference(_ nums: [Int]) -> Int {
        let sorted = nums.sorted()
        return sorted[sorted.count-1] * sorted[sorted.count-2] -  sorted[0] * sorted[1]
    }
}