#include <iostream>#include <cstdlib>#include <cstring>#include <cstdio>using namespace std;#define maxn 1005struct Point{ int x, y;}q[maxn * maxn];int n, m;char map[maxn][maxn];int dist[maxn][maxn];int dir[4][2] = {{1, 0},{0, 1},{-1, 0},{0, -1}};void input(){ scanf("%d%d", &m, &n); for (int i = 0; i < n; i++) scanf("%s", map[i]);}bool in(Point b){ return b.x < n && b.y < m && b.x >= 0 && b.y >= 0;}void bfs(int sx, int sy){ int front = 0; int rear = 0; Point a; a.x = sx; a.y = sy; q[rear++] = a; dist[a.x][a.y] = 0; while (front != rear) { a = q[front++]; if (front == maxn * maxn) front = 0; for (int i= 0; i < 4; i++) { Point b = a; b.x += dir[i][0]; b.y += dir[i][1]; if (in(b) && map[b.x][b.y] == '.' && dist[b.x][b.y] == -1) { dist[b.x][b.y] = dist[a.x][a.y] + 1; q[rear++] = b; if (rear == maxn * maxn) rear = 0; } } }}void work(){ memset(dist, -1, sizeof(dist)); for (int i = 0; i < n; i++) { bool did = false; for (int j = 0; j < m; j++) if (map[i][j] == '.') { bfs(i, j); did = true; break; } if (did) break; } int temp = -1; int sx = 0, sy = 0; for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (dist[i][j] > temp) { temp = dist[i][j]; sx = i; sy = j; } memset(dist, -1, sizeof(dist)); if (temp == -1) { printf("Maximum rope length is %d.n", 0); return; } bfs(sx, sy); temp = -1; for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (dist[i][j] > temp) temp = dist[i][j]; printf("Maximum rope length is %d.n", temp);}int main(){ int t; scanf("%d", &t); while (t--) { input(); work(); } return 0;}
