poj3051

bfs

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
using namespace std;

#define maxw 85
#define maxh 1005

struct Point
{
    int x, y;
    Point(int xx, int yy) :
        x(xx), y(yy)
    {
    }
    Point()
    {
    }
} q[maxw * maxh];

int w, h;
char map[maxh][maxw];
bool vis[maxh][maxw];
int dir[4][2] =
{
{ 1, 0 },
{ 0, 1 },
{ -1, 0 },
{ 0, -1 } };

bool ok(Point &a)
{
    if (a.x < 0 || a.y < 0 || a.x >= h || a.y >= w)
        return false;
    return !vis[a.x][a.y] && map[a.x][a.y] == '*';
}

int bfs(Point a)
{
    int front = 0;
    int rear = 0;
    int ret = 0;

    q[rear++] = a;
    vis[a.x][a.y] = true;
    while (front != rear)
    {
        Point p = q[front++];
        ret++;
        for (int i = 0; i < 4; i++)
        {
            Point b(p.x + dir[i][0], p.y + dir[i][1]);
            if (ok(b))
            {
                vis[b.x][b.y] = true;
                q[rear++] = b;
            }
        }
    }
    return ret;
}

void work()
{
    int ans = 0;
    for (int i = 0; i < h; i++)
        for (int j = 0; j < w; j++)
            if (!vis[i][j] && map[i][j] == '*')
                ans = max(ans, bfs(Point(i, j)));
    printf("%d\n", ans);
}

int main()
{
    //freopen("t.txt", "r", stdin);
    scanf("%d%d", &w, &h);
    for (int i = 0; i < h; i++)
        scanf("%s", map[i]);
    work();
    return 0;
}