1040. 有几个PAT（25）

#include<iostream>
#include<string>
using namespace std;

int main()
{
    string s;
    int NumT=0;
    int NumAT=0;
    int NumPAT=0;
    int Mod = 1000000007;
    cin>>s;
    for( int i=s.size()-1; i>=0; i-- )
    {
        if( s[i]=='T' )
            NumT++;
        else if( s[i]=='A' )
            NumAT = ( NumAT+NumT )%Mod;
        else if( s[i]=='P' )
            NumPAT = ( NumPAT + NumAT )%Mod;
    }
    cout<<NumPAT<<endl;
    return 0;
}