题解 | 牛牛的括号式

#include <iostream>
#include<vector>
using namespace std;
const int MOD=10007;

int main() {
  string s;
  cin>>s;
vector<int>a;
for(int i=0;i<s.length();i++){
if(s[i]=='('&&s[i+1]=='x'){
    char sign=s[i+2];
    char digit=s[i+3];  
    int num=digit-'0';
    if(sign=='-')num=-num;
    num=(num%10007+MOD)%MOD;
    a.push_back(num);
}
}
 int n=a.size();
vector<int>prefix(n);
prefix[0]=a[0];
for(int i=1;i<n;i++) prefix[i]=prefix[i-1]*a[i]%MOD;
vector<int>suffix(n);
suffix[n-1]=a[n-1];
for(int i=n-2;i>=0;i--) suffix[i]=suffix[i+1]*a[i]%MOD;

  
int ans=0;
for(int i=0;i<n;i++){
int left=(i==0?1:prefix[i-1]);
int right=(i==n-1?1:suffix[i+1]);
ans=((ans+left*right)%MOD+MOD)%MOD;
}
cout<<ans<<endl;
}