HDU 1241 Oil Deposits

题目：http://acm.hdu.edu.cn/showproblem.php?pid=1241

给出一张地图，@代表有油，*代表没有。对于一个@，它的上下左右，左上，左下，右上，右下的位置若含有@，则它们属于同一块油田，问给出的地图中有几块油田？

#include<iostream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cstdio>
#include<queue>
#define pii pair<int, int>
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAXN = 107;
int dir[8][2] = {1, 0, -1, 0, 0, 1, 0, -1, 1, 1, 1, -1, -1, 1, -1, -1};
char grid[MAXN][MAXN];
int m, n;
int vis[MAXN][MAXN];
int cnt = 0;
void bfs(int x, int y)
{
    queue<pii> q;
    q.push(pii(x, y));
    while(!q.empty())
    {
        pii now = q.front(); q.pop();
        for(int i = 0; i < 8; i++)
        {
            int nx = now.first + dir[i][0];
            int ny = now.second + dir[i][1];

            if(nx >= 0 && nx < m && ny >= 0 && ny < n
               && grid[nx][ny] != '*' && !vis[nx][ny])
            {
                vis[nx][ny] = 1;
                q.push(pii(nx, ny));
            }
        }
    }
}
int main()
{
    while(cin >> m >> n && (m + n))
    {
        cnt = 0;
        memset(vis, 0, sizeof(vis));
        for(int i = 0; i < m; i++)
            for(int j = 0; j < n; j++)
                cin >> grid[i][j];

        for(int i = 0; i < m; i++)
        {
            for(int j = 0; j < n; j++)
            {
                if(grid[i][j] == '@' && !vis[i][j])
                {
                    cnt++;
                    vis[i][j] = 1;
                    bfs(i, j);
                }
            }
        }
        cout << cnt << endl;
    }
    return 0;
}