题解

#include<bits/stdc++.h>
#define fo(i,a,b) for(int i=a;i<=b;i++)
#define fd(i,a,b) for(int i=a;i>=b;i--)
using namespace std;
const int N=105;
const int mo=1e9+7;
map<string,int> var_map;
int sta[N],n;
int top,tot,cnt;
int hashit(string s)
{
    int &re=var_map[s];
    if (!re)re=++tot;
    return re;
} 
struct matrix
{
    int a[N][N];
    matrix(){}
    matrix(int v)
    {
        memset(a,0,sizeof(a));
        fo(i,0,tot)a[i][i]=v;
    } 
    int* operator [] (int i)
    {
        return a[i];
    } 
    friend matrix operator *(matrix x,matrix y)
    {
        matrix c(0);
         fo(i,0,tot)
         fo(j,0,tot)
         fo(k,0,tot)
         c[i][j]=(c[i][j]+1ll*x[i][k]*y[k][j]%mo)%mo; 
        return c;
    }
    friend matrix pow(matrix a,int b)
    {
        matrix r(1);
        while (b)
        {
            if (b&1)r=r*a;
            a=a*a;
            b>>=1;
        }
        return r;
    }
}mat[N];
int main()
{
    string buffer;
    new(&mat[0])matrix(1);
    while (1)
    {
        static char s[N*5];
        gets(s);
        istringstream stream(s);
        stream>>s;
        if (s[0]>='a'&&s[0]<='z')
        {
            static int b[N];
            int left=hashit(s);
            memset(b,0,sizeof(b));
            while (stream>>s)
            {
                if (s[0]>='a'&&s[0]<='z')
                {
                    int right=hashit(s);
                    fo(i,0,tot)
                    b[i]=(b[i]+mat[top][right][i])%mo;
                }
                else if (s[0]>='0'&&s[0]<='9')
                {
                    int right=atoi(s);
                    b[0]=(b[0]+right)%mo;
                }
            }
            fo(i,0,tot)mat[top][left][i]=b[i];
        }
        else if (s[0]>='0'&&s[0]<='9')
        {
            sta[++top]=atoi(s);
            new (&mat[top])matrix(1);
        }
        else if (s[0]=='}')
        {
            mat[top-1]=pow(mat[top],sta[top])*mat[top-1];
            top--;
        }
        else if (s[0]=='R')
        {
            stream>>s;
            int val=hashit(s);
            int ans=0;
            fo(i,0,tot)ans=(ans+mat[0][val][i])%mo;
            cout<<ans<<'\n';
            break;
        }
    }
    return 0;
}