题解 | 兑换零钱

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int aim = in.nextInt();
            int[] coins = new int[n];
            for (int i=0; i<n; i++) {
                coins[i] = in.nextInt();
            }
            int res = process(coins, aim, n);
            System.out.println(res);
        }
    }


    private static int process(int[] coins, int aim, int n) {
        int[] dp = new int[aim+1];
        Arrays.fill(dp, aim+1);
        dp[0] = 0;

        for (int i=0; i<n; i++) {
            for (int j=coins[i]; j<=aim; j++) {
                dp[j] = Math.min(dp[j], dp[j-coins[i]] + 1);
            }
        }

        return dp[aim] == aim+1 ? -1 : dp[aim];
        
    }
}