题解 | #称砝码#

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Scanner;

/**
 * HJ41 称砝码
 * @author d3y1
 */
public class Main {
    private static int n;
    private static HashSet<Integer> set = new HashSet<>();

    public static void main(String[] args) {
        // solution1();
        solution2();
        // solution3();
    }

    /**
     * dfs: 超时!
     */
    private static void solution1(){
        Scanner in = new Scanner(System.in);
        // 砝码种类
        n = in.nextInt();
        // 砝码重量
        int[] m = new int[n];
        // 砝码数量
        int[] x = new int[n];

        for(int i=0; i<n; i++){
            m[i] = in.nextInt();
        }

        for(int i=0; i<n; i++){
            x[i] = in.nextInt();
        }

        dfs(m, x, 0, 0);

        System.out.println(set.size());
    }

    /**
     * dfs
     * @param m
     * @param x
     * @param idx
     * @param sum
     */
    private static void dfs(int[] m, int[] x, int idx, int sum){
        set.add(sum);

        if(idx == n){
            return;
        }

        // 此处耗时
        for(int i=idx; i<n; i++){
            for(int j=0; j<=x[i]; j++){
                dfs(m, x, i+1, sum+m[i]*j);
            }
        }
    }

    /**
     * 哈希
     */
    private static void solution2(){
        Scanner in = new Scanner(System.in);
        // 砝码种类
        n = in.nextInt();
        // 砝码重量
        int[] m = new int[n];
        // 砝码数量
        int[] x = new int[n];

        for(int i=0; i<n; i++){
            m[i] = in.nextInt();
        }

        for(int i=0; i<n; i++){
            x[i] = in.nextInt();
        }

        set.add(0);
        ArrayList<Integer> weights;
        for(int i=0; i<n; i++){
            weights = new ArrayList<>(set);
            for(int weight: weights){
                for(int j=1; j<=x[i]; j++){
                    set.add(weight+m[i]*j);
                }
            }
        }

        System.out.println(set.size());
    }

    /**
     * 动态规划
     */
    private static void solution3(){
        Scanner in = new Scanner(System.in);
        // 砝码种类
        n = in.nextInt();
        // 砝码重量
        int[] m = new int[n];
        // 砝码数量
        int[] x = new int[n];

        for(int i=0; i<n; i++){
            m[i] = in.nextInt();
        }

        // 总重量
        int sum = 0;
        for(int i=0; i<n; i++){
            x[i] = in.nextInt();
            sum += m[i]*x[i];
        }

        // dp[i]表示砝码能否组成重量i
        boolean[] dp = new boolean[sum+1];
        dp[0] = true;

        for(int i=0; i<n; i++){
            for(int j=1; j<=x[i]; j++){
                // 降序
                for(int k=sum; k>=m[i]; k--){
                    if(dp[k-m[i]]){
                        dp[k] = true;
                    }
                }
            }
        }

        int kind = 0;
        for(int i=0; i<=sum; i++){
            if(dp[i]){
                kind++;
            }
        }

        System.out.println(kind);
    }
}