思路

dp

过程

代码

#include <iostream>
#include <vector>
#include <unordered_map>

using namespace std;

const int N = 1e6;
long long s, h, y;

int n;
string str;

int main()
{
    cin >> n >> str;
    for(int i = 0;i < n;i ++)
    {
        char ch = str[i];
        if(ch == 's') s ++;
        else if(ch == 'h') h += s;
        else if(ch == 'y') y += h;
    }
    cout << y << endl;
    return 0;
}