HDU 1312(BFS)

题意：“.”是red方格，“#”是black方格，“@”是起点。求从起点开始走，可以到达的方格（包括起点），red方格不能走，相当于墙壁。

 

#include 
#include 
#include 
using namespace std;

char map[25][25];
bool visit[25][25];
int count;
const int direction[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};


struct Node
{
    int x, y;
    Node() {}
    Node(int _x, int _y) : x(_x), y(_y) {}
    Node next(int i)
    {
        return Node(x+direction[i][0], y+direction[i][1]);
    }
    bool visit()
    {
        return ::visit[x][y];
    }
    void set()
    {
        ++::count;
        ::visit[x][y] = true;
    }
    bool legal()
    {
        return map[x][y] != '#';
    }
};

int main()
{
    int n, m, i, j, x, y;
    memset(map[0], '#', sizeof map[0]);
    while (scanf("%d%d", &m, &n) != EOF, n || m)
    {
        for (i = 1; i <= n; ++i)
            scanf("%s", map[i]+1), map[i][0] = map[i][m+1] = '#';
        memset(map[n+1], '#', sizeof map[0]);
        memset(visit, false, sizeof visit);
        for (i = 1; i <= n; ++i)
            for (j = 1; j <= m; ++j)
                if (map[i][j] == '@')
                {
                    x = i, y = j;
                }
        ::count = 0;
        queue q;
        q.push(Node(x, y));
        Node(x, y).set();
        Node p, n;
        while (!q.empty())
        {
            p = q.front();
            q.pop();
            for (i = 0; i < 4; ++i)
            {
                n = p.next(i);
                if (!n.legal()) continue;
                if (n.visit()) continue;
                n.set();
                q.push(n);
            }
        }
        printf("%d\n", ::count);
    }
    return 0;
}