C. Greg and Friends

http://codeforces.com/contest/295/problem/C

简单DP

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>

#define ll long long
using namespace std;

const int N=55;
const ll MOD = 1000000007;
ll dp[N*4][N][N];
ll c[N][N];
int main()
{
	//freopen("data.in","r",stdin);
	for(int i=0;i<N;++i)
		for(int j=0;j<=i;++j)
		{
			if(i==j||j==0) c[i][j]=1;
			else c[i][j]=(c[i-1][j-1]+c[i-1][j])%MOD;
		}
	int n,m;
	while(cin>>n>>m)
	{
		int a=0;
		int b=0;
		for(int i=1;i<=n;++i)
		{
			int tmp;
			cin>>tmp;
			if(tmp==50)
				++a;
			if(tmp==100)
				++b;
		}
		memset(dp,0,sizeof(dp));
		dp[0][a][b]=1;
		ll ans=-1;
		int i;
		for(i=0;i<n*4;++i)
		{
			for(int l=0;l<=a;++l)
			{
				for(int r=0;r<=b;++r)
				if(dp[i][l][r]>0)
				{//cout<<i<<" "<<l<<" "<<r<<" "<<dp[i][l][r]<<endl;
					if(l==0&&r==0) {ans=dp[i][l][r];break;}
					int l2=((i&1)==0)?l:a-l;
					int r2=((i&1)==0)?r:b-r;
					for(int l1=0;l1<=l2;++l1)
					for(int r1=0;r1<=r2;++r1)
					{
						if(l1+r1==0||(l1*50+r1*100)>m)continue;
						int w=((i&1)==0)?l-l1:l+l1;
						int h=((i&1)==0)?r-r1:r+r1;
						dp[i+1][w][h]=(dp[i+1][w][h]+((c[l2][l1]*c[r2][r1]%MOD)*dp[i][l][r])%MOD)%MOD;
					}

				}
				if(ans!=-1) break;
			}
			if(ans!=-1) break;
		}
		if(ans==-1)
		{cout<<"-1"<<endl;cout<<"0"<<endl;}
		else
		{cout<<i<<endl;cout<<ans<<endl;}
	}

	return 0;
}