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This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at TikTok.

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This question is commonly asked for Software Engineer candidates at TikTok during technical interviews.

Maximize min+max of contiguous subarray

Company: TikTok

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

You are given an array of **n** positive integers `nums`. Find a **contiguous subarray** that contains **at least two elements** and maximizes the value: > (minimum element of the subarray) + (maximum element of the subarray) Return this maximum possible sum. If multiple subarrays yield the same maximum sum, you only need to return the value of that sum (not the subarray itself). You may assume `n ≥ 2`. --- **Example** Input: ```text nums = [5, 12, 9, 6, 4] ``` All valid subarrays of length ≥ 2 and their `(min + max)` values include: - `[5, 12]` → min = 5, max = 12, sum = 17 - `[5, 12, 9]` → min = 5, max = 12, sum = 17 - `[12, 9]` → min = 9, max = 12, sum = 21 - `[12, 9, 6]` → min = 6, max = 12, sum = 18 - `[9, 6]` → min = 6, max = 9, sum = 15 - ... The maximum possible value of `min + max` is `21`, from subarray `[12, 9]`. **Output:** ```text 21 ```

Quick Answer: This question evaluates understanding of array algorithms and competency in identifying and reasoning about minimum and maximum values within contiguous subarrays, emphasizing extremal value handling.

You are given an array of positive integers nums. Find a contiguous subarray that contains at least two elements and maximizes the value: (minimum element of the subarray) + (maximum element of the subarray). Return this maximum possible sum. If multiple subarrays yield the same maximum sum, return only the value.

Constraints

2 <= len(nums) <= 200000
1 <= nums[i] <= 1000000000

Examples

Input: ([5, 12, 9, 6, 4],)

Expected Output: 21

Explanation: The subarray [12, 9] has min 9 and max 12, giving 21, which is the maximum possible value.

Input: ([3, 8],)

Expected Output: 11

Explanation: There is only one valid subarray, [3, 8], so the answer is 3 + 8 = 11.

Input: ([1, 2, 3, 4, 5],)

Expected Output: 9

Explanation: The best subarray is [4, 5], giving min 4 plus max 5 = 9.

Input: ([10, 1, 10],)

Expected Output: 11

Explanation: The full subarray [10, 1, 10] gives 11, but adjacent subarrays [10, 1] and [1, 10] also give 11.

Input: ([7, 7, 7, 7],)

Expected Output: 14

Explanation: Every valid subarray has min 7 and max 7, so the maximum sum is 14.

Input: ([1000000000, 1, 999999999],)

Expected Output: 1000000001

Explanation: The best adjacent sums are 1000000000 + 1 and 1 + 999999999, so the maximum is 1000000001.

Hints

For any valid subarray, look at where its maximum element is. Since the subarray has at least two elements, that maximum has at least one neighbor inside the subarray.
Can every longer subarray's min + max be matched or exceeded by some adjacent pair inside it?

Quick Overview

This question evaluates understanding of array algorithms and competency in identifying and reasoning about minimum and maximum values within contiguous subarrays, emphasizing extremal value handling.