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$LOJ$ $2833$ $「JOISC 2018 Day 1」$ 帐篷

链接

背景

\(Japan\) \(Olympiad\) \(in\) \(Informatics\) \(Spring\) \(Camp\) \(2018\) \(Day1\) \(T3\)\(LOJ\) \(2833\)

题意

咕咕咕

解法

细节

代码

$View$ $Code$
//省略头文件
using namespace std;
inline int read()
{
    int ret=0,f=1;
    char ch=getchar();
    while(ch>'9'||ch='0'&&ch<='9')
    {
        ret=(ret<<1)+(ret<<3)+ch-'0';
        ch=getchar();
    }
    return ret*f;
}
const int mod=1e9+7;
int h,w,ans;
long long dp[3005][3005];
int main()
{
    h=read();
    w=read();
    for(int i=0;i<=h;i++)
    {
        for(int j=0;j<=w;j++)
        {
            if(!i||!j) 
                dp[i][j]=1;
            else
            {
                dp[i][j]=dp[i][j-1]+4*i*dp[i-1][j-1];
                if(2<=i)
                    dp[i][j]+=i*(i-1)/2*dp[i-2][j-1];
                if(2<=j)
                    dp[i][j]+=i*(j-1)*dp[i-1][j-2];
                dp[i][j]%=mod;
            }
        }
    }
    ans=((dp[h][w]-1)%mod+mod)%mod;
    printf("%d\n",ans);
    return 0;
}

转载于:https://www.cnblogs.com/Peter0701/p/11361014.html

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