dfs36分求调

#include <bits/stdc++.h>
using namespace std;
int r, c, ans;
string a[1001];
int f[1001][1001];

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
void dfs(int x, int y) {
	f[x][y] = 1;
	for (int i = 0; i < 4; i++) {
		int nr = x + dx[i];
		int nc = y + dy[i];
		if (nr < 0 || nr > r || nc < 0 || nc > c || f[nr][nc] == 1) {
			continue;
		}
		dfs(nr, nc);
		f[nr][nc] = 1;
	}
}
int main() {
	cin.tie(0);
	cin >> r >> c;
	for (int i = 0; i < r; i++) {
		cin >> a[i];
	}
	for (int i = 0; i < r; i++) {
		for (int j = 0; j < c; j++) {
			if (a[i][j] == '#') {
				f[i][j] = 0;
			} else {
				f[i][j] = 1;
			}
		}
	}
	for (int i = 0; i < r; i++) {
		for (int j = 0; j < c; j++) {
			if (f[i][j] == 0) {
				ans++;
				dfs(i, j);
			}
		}
	}
	if (ans > 0)
		cout << "There are " << ans << " ships.";
	else
		cout << "Bad placement.";
	return 0;
}