#include <iostream>
#include <string>
using namespace std;
int main() {
string s;
cin >> s;
int len = s.length(), result = 0, count_p = 0, count_t = 0;
for (int i = 0; i < len; i++) {
if (s[i] == 'T')
count_t++;
}
for (int i = 0; i < len; i++) {
if (s[i] == 'P') count_p++;
if (s[i] == 'T') count_t--;
if (s[i] == 'A')
result = (result + (count_p * count_t) % 1000000007) % 1000000007;
}
cout << result;
return 0;
}
方法2
#include <stdio.h>
#define LIM 1000000007
int main()
{
int P = 0, PA = 0, PAT = 0;
char c;
while((c = getchar()) != '\n')
{
if(c == 'P') P++;
if(c == 'A') PA = (PA + P) % LIM;
if(c == 'T') PAT = (PAT + PA) % LIM;
}
printf("%d", PAT);
return 0;
}
