（AtCoder Beginner Contest 375）A - Seats

题目大意

给定一个长度为$N$的字符串$S$
$S$ 只包含"#“和”."
求 "#.#"子串 的出现次数

思路

签到题 $O(N)$ 模拟即可

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<map>
#define rep(i,x,y) for(ll i=x;i<=y;++i)
#define per(i,x,y) for(ll i=x;i>=y;--i)
using namespace std;
typedef long long ll;
string s;
ll n,ans; 
inline ll in()
{
    ll res=0,f=1;
    char ch;
    while((ch=getchar())<'0'||ch>'9')
     if(ch=='-') f=-1;
    res=res*10+ch-'0';
    while((ch=getchar())>='0'&&ch<='9')
     res=res*10+ch-'0';
    return res*f;
}
inline void put(ll x)
{
    if(x<0) putchar('-'),x*=-1;
    if(x>9) put(x/10);
    putchar(x%10+48);
}
int main()
{
	n=in();
	cin>>s;
	rep(i,1,n-2)
	 if(s[i]=='.'&&s[i+1]=='#'&&s[i-1]=='#') ++ans;
	cout<<ans;
    return 0;
}