hdu 1429 priority_queue+bfs

#include <iostream>
#include <queue>
using namespace std;

int n, m, t;
char map[20][20];
int dir[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};
bool hash[20][20][1100];
int keybin[10] = {1,2,4,8,16,32,64,128,256,512};

struct Node
{
    short x, y, step, keystate;
    bool key[10];
};

bool operator < (Node a, Node b)
{
    return a.step > b.step;
}

Node first, next;
void init()
{
    int i, j;
    for (i = 0; i < n; ++i)
    {
        getchar();
        for (j = 0; j < m; ++j)
        {
            scanf("%c", &map[i][j]);
            if (map[i][j] == '@')
            {
                first.x = i;
                first.y = j;
            }
        }
    }
    memset(first.key, 0, sizeof(first.key));
    memset(hash, 0, sizeof(hash));
    first.step = 0;
    first.keystate = 0;
}

int bfs()
{
    priority_queue <Node> Q;
    Q.push(first);

    while (!Q.empty())
    {
        first = Q.top();
        Q.pop();

        if (map[first.x][first.y] == '^')
        {
            return first.step;
        }
        if (first.step >= t)//*if not then get a TLE
        {
            return -1;
        }
        for (int i = 0; i < 4; ++i)
        {
            next = first;
            next.x = first.x + dir[i][0];
            next.y = first.y + dir[i][1];
            next.step = first.step + 1;
            if (next.x >= 0 && next.x < n && next.y >= 0 && next.y < m
                && map[next.x][next.y] != '*')
            {
                if (map[next.x][next.y] >= 'A' && map[next.x][next.y] <= 'J')
                {
                    if (first.key[map[next.x][next.y]-'A'] &&
                        !hash[next.x][next.y][next.keystate])
                    {
                        hash[next.x][next.y][next.keystate] = true;
                        Q.push(next);
                    }
                }
                else if (map[next.x][next.y] >= 'a' && map[next.x][next.y] <= 'j')
                {
                    int state = next.keystate, k;
                    k = map[next.x][next.y]-'a';
                    if (!next.key[k])
                    {
                        state += keybin[k];
                    }
                    if (!hash[next.x][next.y][state])
                    {
                        hash[next.x][next.y][state] = true;
                        next.key[k] = true;
                        next.keystate = state;
                        Q.push(next);
                    }
                   
                }
                else
                {
                    if (!hash[next.x][next.y][next.keystate])
                    {
                        hash[next.x][next.y][next.keystate] = true;
                        Q.push(next);
                    }
                }
            }
        }
    }
    return -1;
}
int main()
{
    while (scanf("%d %d %d", &n, &m, &t) != EOF)
    {
        init();
        int result = bfs();
        if (result == -1 || result >= t)
        {
            puts("-1");
        }
        else
        {
            printf("%d\n", result);
        }
    }
    return 0;
}