AcWing 1884. COW 经典dp

Posted 2022-03-11 karshey

AcWing 1884. COW
打卡

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e5+10;
ll ans;
int n;
string a;
int c,o,w;//o代表前面有几个co 
int main()

	cin>>n>>a;
	for(int i=0;a[i];i++)
	
		if(a[i]=='C') c++;
		else if(a[i]=='O') o+=c;
		else ans+=o;//有几个co就有几个cow 
	
	cout<<ans;
	return 0;