poj1979

简单题

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

#define maxn 25

struct XPoint
{
    int x, y;
} a;

bool map[maxn][maxn], vis[maxn][maxn];
int n, m, ans;
int dir[4][2] =
{
{ 0, 1 },
{ 0, -1 },
{ 1, 0 },
{ -1, 0 } };

void input()
{
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            char ch;
            scanf("%c", &ch);
            if (ch == '#')
                map[i][j] = false;
            else
                map[i][j] = true;
            if (ch == '@')
            {
                a.x = i;
                a.y = j;
            }
        }
        getchar();
    }
}

bool ok(XPoint &a)
{
    if (a.x < 0 || a.y < 0 || a.x >= n || a.y >= m)
        return false;
    return !vis[a.x][a.y] && map[a.x][a.y];
}

void bfs()
{
    memset(vis, 0, sizeof(vis));
    queue<XPoint> q;
    q.push(a);
    vis[a.x][a.y] = true;
    ans = 0;
    while (!q.empty())
    {
        XPoint a = q.front();
        q.pop();
        ans++;
        XPoint b;
        for (int i = 0; i < 4; i++)
        {
            b.x = a.x + dir[i][0];
            b.y = a.y + dir[i][1];
            if (ok(b))
            {
                q.push(b);
                vis[b.x][b.y] = true;
            }
        }
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d%d", &m, &n), m | n)
    {
        getchar();
        input();
        bfs();
        printf("%d\n", ans);
    }
    return 0;
}