3584. Maximum Product of First and Last Elements of a Subsequence

Problem Link

Description

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You are given an integer array nums and an integer m.

Return the maximum product of the first and last elements of any subsequence of nums of size m.

 

Example 1:

Input: nums = [-1,-9,2,3,-2,-3,1], m = 1

Output: 81

Explanation:

The subsequence [-9] has the largest product of the first and last elements: -9 * -9 = 81. Therefore, the answer is 81.

Example 2:

Input: nums = [1,3,-5,5,6,-4], m = 3

Output: 20

Explanation:

The subsequence [-5, 6, -4] has the largest product of the first and last elements.

Example 3:

Input: nums = [2,-1,2,-6,5,2,-5,7], m = 2

Output: 35

Explanation:

The subsequence [5, 7] has the largest product of the first and last elements.

 

Constraints:

• 1 <= nums.length <= 105
• -105 <= nums[i] <= 105
• 1 <= m <= nums.length

Solution

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Python3

class Solution:
    def maximumProduct(self, nums: List[int], m: int) -> int:
        N = len(nums)
        maxVal, minVal = -inf, inf
        res = -inf
 
        for i, x in enumerate(nums):
            if i >= m - 1:
                maxVal = max(maxVal, nums[i - m + 1])
                minVal = min(minVal, nums[i - m + 1])
 
                res = max(res, x * maxVal, x * minVal)
 
        return res