购买苹果的最低成本

/*
 * Leetcode 2473: Minimum Cost to Buy Apples
 * Problem: Given a list of prices for different quantities of apples, determine the minimum cost to buy exactly n apples.
 * 
 * Approach:
 * 1. Use a dynamic programming (DP) array to store the minimum cost for each number of apples from 0 to n.
 * 2. Initialize the DP array with a large value (e.g., Integer.MAX_VALUE) except dp[0] which should be 0 (cost of 0 apples is 0).
 * 3. For each quantity-price pair, update the DP array by considering the minimum cost for the current quantity of apples plus the cost of the current price.
 * 4. Return the minimum cost to buy exactly n apples.
 * 5. Use Java Streams where applicable to streamline the process.
 */
import java.util.*;
import java.util.stream.*;

public class Solution {
    public int minCostToBuyApples(int n, int[][] prices) {
        int[] dp = new int[n + 1];
        Arrays.fill(dp, Integer.MAX_VALUE);
        dp[0] = 0;

        Arrays.stream(prices).forEach(price -> {
            int quantity = price[0];
            int cost = price[1];
            IntStream.rangeClosed(quantity, n).forEach(i -> {
                if (dp[i - quantity] != Integer.MAX_VALUE) {
                    dp[i] = Math.min(dp[i], dp[i - quantity] + cost);
                }
            });
        });

        return dp[n] == Integer.MAX_VALUE ? -1 : dp[n];
    }
}