正经题解|Drogon

思维水题，建议评红

#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;
const int N=1e6+5;
int a[N];
long long l[N],r[N];
int main() {
	int n,cnt=0;
	scanf("%d",&n);
	for (int i=1;i<=n;i++) {
		char ch;
		cin>>ch;
		if (ch=='*') {
			a[i]=1;
		}
		cnt+=a[i];
		l[i]=l[i-1];
		if (a[i]==0) {
			l[i]+=cnt;
		}
	}
	cnt=0;
	long long ans=1e18;
	for (int i=n;i>=1;i--) {
		cnt+=a[i];
		r[i]=r[i+1];
		if (a[i]==0) {
			r[i]+=cnt;
		}
		ans=min(ans,l[i-1]+r[i]);
	}
	printf("%lld",ans);
	return 0;
}