题解 | 数位五五

using System;
public class Program
{
    public static int Sum(int n)//求各位数之和
    {
        int sum = 0;
        while (n > 0)
        {
            sum += n % 10;
            n /= 10;
        }
        return sum;
    }

    public static int Count(string s1, string s2)//求5的倍数的数量
    {
        int count = 0;
        int n1 = int.Parse(s1);
        int n2 = int.Parse(s2);
        for (int i = n1; i <= n2; i++)
        {
            if (Sum(i) % 5 == 0)
                count++;
        }
        return count;
    }

    public static void Main()
    {
        string[] str = Console.ReadLine().Split();
        int num = Count(str[0], str[1]);
        Console.WriteLine(num);
    }
}