README.md

1561. Maximum Number of Coins You Can Get

Tag: Array & String Sorting

Difficulty: Medium

There are $3^n$ piles of coins of varying size, you and your friends will take piles of coins as follows:

• In each step, you will choose any 3 piles of coins (not necessarily consecutive).
• Of your choice, Alice will pick the pile with the maximum number of coins.
• You will pick the next pile with the maximum number of coins.
• Your friend Bob will pick the last pile.
• Repeat until there are no more piles of coins.

Given an array of integers piles where piles[i] is the number of coins in the $i^{th}$ pile.

Return the maximum number of coins that you can have.

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Example 1:

Input: piles = [2,4,1,2,7,8]
Output: 9
Explanation: Choose the triplet (2, 7, 8), Alice Pick the pile with 8 coins, you the pile with 7 coins and Bob the last one.
Choose the triplet (1, 2, 4), Alice Pick the pile with 4 coins, you the pile with 2 coins and Bob the last one.
The maximum number of coins which you can have are: 7 + 2 = 9.
On the other hand if we choose this arrangement (1, 2, 8), (2, 4, 7) you only get 2 + 4 = 6 coins which is not optimal.

Example 2:

Input: piles = [2,4,5]
Output: 4

Example 3:

Input: piles = [9,8,7,6,5,1,2,3,4]
Output: 18

Constraints:

• $3 \le piles.length \le 10^5$
• $piles.length % 3 == 0$
• $1 \le piles[i] \le 10^4$

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Sorting

class Solution:
    def maxCoins(self, piles: List[int]) -> int:
        # Time Limit Exceeded
        piles.sort()
        ans = 0

        while piles:
            alice = piles.pop()
            ans += piles.pop()
            piles = piles[1:]

        return ans