ZOJ 1649 BFS

#include <cstdio>
#include <queue>
#include <cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 2E2 + 10;
const int dir[4][2] = {{0, 1}, {0, -1}, {1, 0}, { -1, 0}};
struct Node
{
    int x, y;
    int step;
    bool operator<(const Node &oth)const
    {
        return step > oth.step;
    }
};
Node cur, Next;
char mp[maxn][maxn];
int n, m, Arrival[maxn][maxn], Startx, Starty;
int BFS()
{
    priority_queue<Node>Q;
    cur.x = Startx; cur.y = Starty; cur.step = 0;
    Arrival[Startx][Starty] = 0;
    Q.push(cur);
    while (!Q.empty())
    {
        cur = Q.top(); Q.pop();
        if (mp[cur.x][cur.y] == 'a') return cur.step;
        for (int i = 0; i < 4; i++)
        {
            Next.x = cur.x + dir[i][0];
            Next.y = cur.y + dir[i][1];
            Next.step = cur.step + 1;
            if (mp[Next.x][Next.y] == 'x') Next.step++;
            if (mp[Next.x][Next.y] != '#' && Next.step < Arrival[Next.x][Next.y])
            {
                Arrival[Next.x][Next.y] = Next.step;
                Q.push(Next);
            }
        }
    }
    return 0;
}
int main(int argc, char const *argv[])
{
    while (~scanf("%d%d", &n, &m))
    {
        for (int i = 0; i <= m + 1; i++)
            mp[0][i] = mp[n + 1][i] = '#';
        for (int i = 1; i <= n; i++)
        {
            scanf("%s", mp[i] + 1);
            mp[i][0] = mp[i][m + 1] = '#';
            for (int j = 1; j <= m; j++)
                if (mp[i][j] == 'r') Startx = i, Starty = j;
        }
        memset(Arrival, INF, sizeof(Arrival));
        int ans = BFS();
        if (ans) printf("%d\n", ans);
        else printf("Poor ANGEL has to stay in the prison all his life.\n");
    }
    return 0;
}

这题简直有鬼。。。