21 lines
409 B
C++
21 lines
409 B
C++
// lanqiao3514 字串简写(前缀和优化)
|
|
#include<bits/stdc++.h>
|
|
using namespace std;
|
|
#define int long long
|
|
signed main(){
|
|
int k;
|
|
string s;
|
|
char a, b;
|
|
cin >> k >> s >> a >> b;
|
|
int ft = 0;
|
|
int bk = 0;
|
|
for(int i = 0, j = k - 1; j < s.size(); i++, j++){
|
|
if(s[i] == a) ft++;
|
|
if(s[j] == b) bk += ft;
|
|
}
|
|
cout << bk << endl;
|
|
}
|
|
/* samples -> 6
|
|
4
|
|
abababdb a b
|
|
*/ |