题解

#include <bits/stdc++.h>
using namespace std;

int main() {
int n, m;
cin >> n >> m;
char a[1005][1005];
int c[1005][1005] = {0};

for (int i = 1; i <= n; i++) {
	for (int j = 1; j <= m; j++) {
		cin >> a[i][j];
	}
}

int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};
int t = 0;

for (int i = 1; i <= n; i++) {
	for (int j = 1; j <= m; j++) {
		if (a[i][j] == '.') {
			bool c1 = true;
			for (int d = 0; d < 4; d++) {
				int ni = i + dx[d];
				int nj = j + dy[d];
				if ( a[ni][nj] == '#') {
					c1 = false;
					break;
				}
			}
			if (c1) {
				t++;
				for (int d = 0; d < 4; d++) {
					int ni = i + dx[d];
					int nj = j + dy[d];
					c[ni][nj]++;
				}
				c[i][j]++;
			}
		}
	}
}

if (t == 0) {
	cout << 0 << endl;
	return 0;
}

int max1 = 0;
for (int i = 1; i <= n; i++) {
	for (int j = 1; j <= m; j++) {
		if (a[i][j] == '.') {
			max1 = max(max1, c[i][j]);
		}
	}
}

cout << t - max1 << endl;
return 0;

}