1040 有几个PAT (25分)
https://pintia.cn/problem-sets/994805260223102976/problems/994805282389999616
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <cstring>
typedef long long ll;
using namespace std;
int main()
{
ll sum=0,cou_p=0,cou_t=0;
string str;
cin>>str;
for(int i=0;i<str.length();i++)
if(str[i]=='T') cou_t++;
for(int i=0;i<str.length();i++)
{
if(str[i]=='P') cou_p++;
else if(str[i]=='T') cou_t--;
else if(str[i]=='A')
sum+=(cou_p*cou_t);
}
printf("%d
",sum%1000000007);
return 0;
}