题解 | #称砝码#

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        long size = long.Parse(Console.ReadLine().Trim());
        long[] weightArray = Console.ReadLine().Trim().Split(' ').ToArray().Select(s => long.Parse(s)).ToArray();
        long[] countArray = Console.ReadLine().Trim().Split(' ').ToArray().Select(s => long.Parse(s)).ToArray();
        Dictionary<long,List<long>>dic = new Dictionary<long,List<long>>();
        for (long i = 0; i < size; i++)
        {
            long weight = weightArray[i];
            long count = countArray[i];
            List<long> list = new List<long>();
            //可能是0-n个
            for (long n = 0; n <= count; n++)
            {
                list.Add(weight * n);
            }
            dic.Add(weight, list);
        }
        HashSet<long> resultSet = new HashSet<long>();
        foreach (var item in dic)
        {
            HashSet<long> childSet = item.Value.ToHashSet();
            MergeHashSet(resultSet, childSet);
        }
        System.Console.WriteLine(resultSet.Count);
    }

    public static void MergeHashSet(HashSet<long> fullSet, HashSet<long> childSet)
    {
       HashSet<long> tempSet= fullSet.ToHashSet();
       foreach (var big in tempSet)
        {
            foreach (var small in childSet)
            {
                fullSet.Add(big+small);
            }
        }
        foreach (var small in childSet)
        {
            fullSet.Add(small);
        }
    }
    
}