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Stone Game VIII

Alice and Bob take turns playing a game, with Alice starting first.

Alice and Bob take turns playing a game, with Alice starting first.

There are n stones arranged in a row. On each player's turn, while the number of stones is more than one, they will do the following:

The game stops when only one stone is left in the row.

The score difference between Alice and Bob is (Alice's score - Bob's score). Alice's goal is to maximize the score difference, and Bob's goal is the minimize the score difference.

Given an integer array stones of length n where stones[i] represents the value of the ith stone from the left, return the score difference between Alice and Bob if they both play optimally.

Stone Game VIII diagram

Example 1

Input: stones = [-1,2,-3,4,-5]

Output: 5

Explanation: - Alice removes the first 4 stones, adds (-1) + 2 + (-3) + 4 = 2 to her score, and places a stone of value 2 on the left. stones = [2,-5]. - Bob removes the first 2 stones, adds 2 + (-5) = -3 to his score, and places a stone of value -3 on the left. stones = [-3]. The difference between their scores is 2 - (-3) = 5.

Example 2

Input: stones = [7,-6,5,10,5,-2,-6]

Output: 13

Explanation: - Alice removes all stones, adds 7 + (-6) + 5 + 10 + 5 + (-2) + (-6) = 13 to her score, and places a stone of value 13 on the left. stones = [13]. The difference between their scores is 13 - 0 = 13.

Example 3

Input: stones = [-10,-12]

Output: -22

Explanation: - Alice can only make one move, which is to remove both stones. She adds (-10) + (-12) = -22 to her score and places a stone of value -22 on the left. stones = [-22]. The difference between their scores is (-22) - 0 = -22.

Constraints

  • n == stones.length
  • 2 <= n <= 10^5
  • -10^4 <= stones[i] <= 10^4

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