LeetCode 2218: Maximum Value of K Coins From Piles Solution

Master LeetCode problem 2218 (Maximum Value of K Coins From Piles), a hard challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2218. Maximum Value of K Coins From Piles

Hard

Array Dynamic Programming Prefix Sum

Problem Explanation

Explanation

To solve this problem, we need to maximize the total value of coins we can obtain by choosing exactly k coins. We can achieve this by sorting the coins in each pile in descending order and then greedily picking the top coin from each pile in a way that maximizes our total value. We start by choosing the top k coins from the first pile, then iteratively choose the top coin from the pile with the highest remaining value until we have chosen k coins.

Algorithm:

Sort all piles in descending order based on the values of coins.
Initialize the total value variable to 0.
Iterate over the piles and greedily choose the top coin from each pile until we have chosen k coins.
Return the total value obtained.

Time Complexity:

The time complexity of this algorithm is O(n * log(n)) where n is the total number of coins in all piles, as we sort each pile.

Space Complexity:

The space complexity is O(n) for storing the sorted piles.

Solution Code

import java.util.Arrays;

class Solution {
    public int maxCoins(int[][] piles, int k) {
        Arrays.sort(piles, (a, b) -> b[0] - a[0]);
        
        int totalValue = 0;
        int remaining = k;
        
        for (int i = 0; i < piles.length && remaining > 0; i++) {
            totalValue += piles[i][0];
            remaining--;
        }
        
        return totalValue;
    }
}

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