3847. Find the Score Difference in a Game - Solution & Explanation

Problem Statement

You are given an integer array nums, where nums[i] represents the points scored in the i^th game.

There are exactly two players. Initially, the first player is active and the second player is inactive.

The following rules apply sequentially for each game i:

If nums[i] is odd, the active and inactive players swap roles.
In every 6th game (that is, game indices 5, 11, 17, ...), the active and inactive players swap roles.
The active player plays the i^th game and gains nums[i] points.

Return the score difference, defined as the first player's total score minus the second player's total score.

Example 1:

Input: nums = [1,2,3]

Output: 0

Explanation:

Game 0: Since the points are odd, the second player becomes active and gains nums[0] = 1 point.
Game 1: No swap occurs. The second player gains nums[1] = 2 points.
Game 2: Since the points are odd, the first player becomes active and gains nums[2] = 3 points.
The score difference is 3 - 3 = 0.

Example 2:

Input: nums = [2,4,2,1,2,1]

Output: 4

Explanation:

Games 0 to 2: The first player gains 2 + 4 + 2 = 8 points.
Game 3: Since the points are odd, the second player is now active and gains nums[3] = 1 point.
Game 4: The second player gains nums[4] = 2 points.
Game 5: Since the points are odd, the players swap roles. Then, because this is the 6th game, the players swap again. The second player gains nums[5] = 1 point.
The score difference is 8 - 4 = 4.

Example 3:

Input: nums = [1]

Output: -1

Explanation:

Game 0: Since the points are odd, the second player is now active and gains nums[0] = 1 point.
The score difference is 0 - 1 = -1.

Constraints:

Solutions for this problem are being prepared.