BZOJ 4778 Usaco2017 Open COWBASIC 矩阵乘法

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题目大意：自己看= =

容易发现所有的变换都是线性变换，用矩乘模拟

循环那个用个栈来模拟嵌套关系就行了

#include <map>#include <string>#include <cstdio>#include <cstring>#include <sstream>#include <iostream>#include <algorithm>#define M 110#define MOD 1000000007using namespace std;map<string,int> var_map;int stack[M],top;int tot;int Hash(string s){    int &re=var_map[s];    if(!re) re=++tot;    return re;}struct Matrix{    int a[M][M];    Matrix() {}    Matrix(int val)    {        memset(a,0,sizeof a);        for(int i=0;i<=tot;i++)            a[i][i]=val;    }    int* operator [] (int i)    {        return a[i];    }    friend Matrix operator * (Matrix x,Matrix y)    {        Matrix z(0);        for(int i=0;i<=tot;i++)            for(int j=0;j<=tot;j++)                for(int k=0;k<=tot;k++)                    (z[i][j]+=(long long)x[i][k]*y[k][j]%MOD)%=MOD;        return z;    }    friend Matrix Quick_Power(Matrix x,int y)    {        Matrix re(1);        while(y)        {            if(y&1) re=re*x;            x=x*x; y>>=1;        }        return re;    }}matrix[M];int main(){    string buffer;    new (&matrix[0])Matrix(1);    while(1)    {        static char s[360];        gets(s);        istringstream stream(s);        stream>>s;        if(s[0]>='a'&&s[0]<='z')        {            static int b[M];            int left=Hash(s);            memset(b,0,sizeof b);            while(stream>>s)            {                if(s[0]>='a'&&s[0]<='z')                {                    int right=Hash(s);                    for(int i=0;i<=tot;i++)                        (b[i]+=matrix[top][right][i])%=MOD;                }                else if(s[0]>='0'&&s[0]<='9')                {                    int right=atoi(s);                    (b[0]+=right)%=MOD;                }            }            for(int i=0;i<=tot;i++)                matrix[top][left][i]=b[i];        }        else if(s[0]>='0'&&s[0]<='9')        {            stack[++top]=atoi(s);            new (&matrix[top])Matrix(1);        }        else if(s[0]=='}')        {            matrix[top-1]=Quick_Power(matrix[top],stack[top])*matrix[top-1];            top--;        }        else if(s[0]=='R')        {            stream>>s;            int val=Hash(s);            int ans=0;            for(int i=0;i<=tot;i++)                (ans+=matrix[0][val][i])%=MOD;            cout<<ans<<endl;            break;        }    }    return 0;}

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