题目解析

解析：求PAT总数，要先将问题拆分先求有效PA总数
从左遍历字符串，遇到P就累计P数量，A前面有效的P的数量就是pacount+=pcount;T同理

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String text = in.nextLine();
        int pcount = 0;
        int pacount= 0;
        int totalcount = 0;
        for (int i=0;i<text.length();i++){
             char c = text.charAt(i);
            if (c == 'P') {
                pcount++;
            } else if (c == 'A') {
                pacount+=pcount;
            }else {
                totalcount+=pacount;
                totalcount %= 1000000007;
            }
        }
        System.out.println(totalcount);
    }
}