NYOJ VF

VF

时间限制：1000 ms  |  内存限制：65535 KB

难度：2

描述

Vasya is the beginning mathematician. He decided to make an important contribution to the science and to become famous all over the world. But how can he do that if the most interesting facts such as
Pythagor’s theorem are already proved? Correct! He is to think out something his own, original. So he thought out the Theory of Vasya’s Functions. Vasya’s Functions (VF) are rather simple: the value of the Nth VF
in the point S is an amount of integers from 1 to N that have the sum of digits S. You seem to be great programmers, so Vasya gave you a task to find the milliard VF value (i.e. the VF with N = 109)
because Vasya himself won’t cope with the task. Can you solve the problem?

输入

There are multiple test cases.

Integer S (1 ≤ S ≤ 81).

输出

The milliard VF value in the point S.

样例输入

1

样例输出

10

我的代码：

#include <iostream>
#include <cstring>
using namespace std;
int main()
{
	int n,i,j,k;
	int dp[10][82];
	memset(dp,0,sizeof(dp));
	for (i=1;i<=9;++i)
	{
		dp[1][i]=1;
	}
	for (i=1;i<=9;++i)//总的位数
	{
		for (j=1;j<=i*9;++j)//在i位下的j值
		{
			for (k=0;k<=9&&k<=j;++k)//没次的前一位都由后一位决定
			{
				dp[i][j]+=dp[i-1][j-k];//因为j>k，所以j可取j-k的数来组成j
			}
		}
	}
	while (cin >> n)
	{
		int sum;
		if (n==1)
		{
			cout << 10 << endl;
			continue;
		}
		for (i=1,sum=0;i<=9;++i)
		{
			sum+=dp[i][n] ;
		}
		cout << sum << endl;
	}
	return 0;
}