牛客网PAT练习场-有几个PAT

题目地址：https://www.nowcoder.com/pat/6/problem/4066

题意：求pat->求pa->求p

 1 /**
 2 *
 3 *作者:YCute
 4 *时间:2019-12-05-16.02.54
 5 *题目题意简单描述:DP，求pat-》先求pa-》求p
 6 */
 7 
 8 
 9 #include<iostream>
10 #include<cmath>
11 #include<cstring>
12 #include<algorithm>
13 #include<vector>
14 using namespace std;
15 int main(){
16     int ch;
17     int sum=0;
18     int sum1=0;
19     int sum2=0;
20     while(scanf("%c",&ch)!=EOF){
21         if(ch=='P'){
22             ++sum;
23         }else if(ch=='A'){
24             sum1+=sum;
25             sum1=sum1%1000000007;
26         }else if(ch=='T'){
27             sum2+=sum1;
28             sum2=sum2%1000000007;
29         }
30     }
31     printf("%d\n",sum2);
32     return 0;
33 }