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Compute Score Difference in Reversing Array Game

Quick Overview

This question evaluates array manipulation and stateful simulation skills, parity-based control flow reasoning, and the ability to analyze time complexity within the Coding & Algorithms domain. It is commonly asked to test handling of sequential state updates and edge cases (such as empty inputs) and requires practical implementation-level thinking rather than purely conceptual reasoning.

Compute Score Difference in Reversing Array Game

Company: Adia

Role: Data Scientist

Category: Coding & Algorithms

Difficulty: easy

Interview Round: Technical Screen

You are given an array of integers. Repeatedly remove the first element of the current array until it becomes empty. Scoring rules: - If the removed number is even, add it to Player 1's score. - If the removed number is odd, add it to Player 2's score, then reverse the remaining array before continuing. Return the final score difference: `Player 1 score - Player 2 score`. Clarify the algorithm, handle edge cases such as an empty array, and analyze the time complexity.

Quick Answer: This question evaluates array manipulation and stateful simulation skills, parity-based control flow reasoning, and the ability to analyze time complexity within the Coding & Algorithms domain. It is commonly asked to test handling of sequential state updates and edge cases (such as empty inputs) and requires practical implementation-level thinking rather than purely conceptual reasoning.

You are given an integer array `nums`. Repeatedly remove the first element of the current array until the array becomes empty. Scoring rules: - If the removed number is even, add it to Player 1's score. - If the removed number is odd, add it to Player 2's score, then reverse the remaining array before continuing. Return the final score difference: `Player 1 score - Player 2 score`. Important: Reversing the remaining array after every odd value can be too slow for large inputs. Think carefully about how to simulate the process efficiently. Edge cases: - If the array is empty, return `0`. - Negative numbers should follow the same even/odd rules as positive numbers.

Constraints

0 <= len(nums) <= 200000
-1000000000 <= nums[i] <= 1000000000

Examples

Input: ([],)

Expected Output: 0

Explanation: The array is empty, so no turns are played and both scores stay 0.

Input: ([7],)

Expected Output: -7

Explanation: 7 is odd, so Player 2 gets 7 points. Reversing an empty remainder has no effect. Final difference is 0 - 7 = -7.

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

Expected Output: 3

Explanation: Remove 2 -> Player 1 = 2. Remove 3 -> Player 2 = 3, reverse [4]. Remove 4 -> Player 1 = 6. Final difference is 6 - 3 = 3.

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

Expected Output: 2

Explanation: Remove 1 -> Player 2 = 1, reverse [2,3,4] to [4,3,2]. Remove 4 -> Player 1 = 4. Remove 3 -> Player 2 = 4, reverse [2]. Remove 2 -> Player 1 = 6. Final difference is 6 - 4 = 2.

Input: ([-1, -2, -3],)

Expected Output: 2

Explanation: Remove -1 -> Player 2 = -1, reverse [-2,-3] to [-3,-2]. Remove -3 -> Player 2 = -4, reverse [-2]. Remove -2 -> Player 1 = -2. Final difference is -2 - (-4) = 2.

Input: ([5, 2, 7, 8, 1],)

Expected Output: -3

Explanation: Remove 5 -> Player 2 = 5, reverse to [1,8,7,2]. Remove 1 -> Player 2 = 6, reverse to [2,7,8]. Remove 2 -> Player 1 = 2. Remove 7 -> Player 2 = 13, reverse [8]. Remove 8 -> Player 1 = 10. Final difference is 10 - 13 = -3.

Hints

After several reversals, the current 'front' of the array is always at one of the two ends of the remaining segment.
Instead of actually reversing the array, track the current direction with a boolean flag and move two pointers.

Last updated: Jun 6, 2026

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Quick Overview

Compute Score Difference in Reversing Array Game

Company: Adia

Role: Data Scientist

Category: Coding & Algorithms

Difficulty: easy

Interview Round: Technical Screen

Constraints

0 <= len(nums) <= 200000
-1000000000 <= nums[i] <= 1000000000

Examples

Input: ([],)

Expected Output: 0

Explanation: The array is empty, so no turns are played and both scores stay 0.

Input: ([7],)

Expected Output: -7

Explanation: 7 is odd, so Player 2 gets 7 points. Reversing an empty remainder has no effect. Final difference is 0 - 7 = -7.

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

Expected Output: 3

Explanation: Remove 2 -> Player 1 = 2. Remove 3 -> Player 2 = 3, reverse [4]. Remove 4 -> Player 1 = 6. Final difference is 6 - 3 = 3.

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

Expected Output: 2

Explanation: Remove 1 -> Player 2 = 1, reverse [2,3,4] to [4,3,2]. Remove 4 -> Player 1 = 4. Remove 3 -> Player 2 = 4, reverse [2]. Remove 2 -> Player 1 = 6. Final difference is 6 - 4 = 2.

Input: ([-1, -2, -3],)

Expected Output: 2

Explanation: Remove -1 -> Player 2 = -1, reverse [-2,-3] to [-3,-2]. Remove -3 -> Player 2 = -4, reverse [-2]. Remove -2 -> Player 1 = -2. Final difference is -2 - (-4) = 2.

Input: ([5, 2, 7, 8, 1],)

Expected Output: -3

Hints

After several reversals, the current 'front' of the array is always at one of the two ends of the remaining segment.
Instead of actually reversing the array, track the current direction with a boolean flag and move two pointers.

Last updated: Jun 6, 2026

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