hdu 1180

地址：http://acm.hdu.edu.cn/showproblem.php?pid=1180

题意：中文。

mark：题目没说明楼梯改变情况。sample中的路径应该是先向上走，再向右走，通过楼梯后走到头再向上，这里wa了1次。

bfs+优先队列。优先队列用手写堆实现。数据规模很小。

代码：

# include <stdio.h>
# include <string.h>


char graph[25][25] ;
int dr[4][2] = {0,1,0,-1,1,0,-1,0} ;
int sx, sy, ex, ey ;
int vis[25][25] ;
int q[25*25*10][3], qcnt ;
int n, m ;


void swap(int a[3], int b[3])
{
    int i, t ;
    for( i = 0 ; i < 3 ; i++)
        t = a[i], a[i] = b[i], b[i] = t ;
}


void qpush(int x, int y, int t)
{
    int idx = qcnt++ ;
    q[idx][0] = x, q[idx][1] = y, q[idx][2] = t ;    
    while (idx != 1)
    {
        if (q[idx][2] < q[idx/2][2])
            swap(q[idx], q[idx/2]) ;
        else break ;
        idx /= 2 ;
    }
}


void heapify(int idx)
{
    int l = idx*2, r=idx*2+1, least = idx ;
    if (l<qcnt && q[l][2]<q[least][2])
        least = l ;
    if (r<qcnt && q[r][2]<q[least][2])
        least = r ;
    if (least == idx) return ;
    swap(q[least], q[idx]) ;
    heapify(least) ;
}


void qpop(int *px, int *py, int *pt)
{
    *px = q[1][0], *py = q[1][1], *pt = q[1][2] ;
    swap(q[1], q[--qcnt]) ;
    heapify(1) ;
}


int bfs()
{
    int i, front = 0, rear = 2 ;
    int x, y, t, xx, yy ;
    vis[sx][sy] = 1 ;
    qpush(sx, sy, 0) ;
    qpush(sx, sy, 1) ;
    while (qcnt != 1)
    {
        qpop(&x, &y, &t) ;
        printf ("%d %d %d\n", x, y, t) ;
        if (x == ex && y == ey) return t ;
        for(i = 0 ; i < n ;i++)
        {
            xx = x + dr[i][0], yy = y + dr[i][1] ;
            if (xx < 0 || xx >= n) continue ;
            if (yy < 0 || yy >= m) continue ;    
            //楼梯改变坐标
            if (graph[xx][yy] == '-' || graph[xx][yy] == '|')
            {
                if (i>=2) //左右 
                {
                    if (((t%2 == 0) && (graph[xx][yy] == '|')) ||
                        ((t%2 == 1) && (graph[xx][yy] == '-')))
                    {
                        xx += dr[i][0] ;
                        yy += dr[i][1] ;
                    }
                    else continue ;
                }
                else //上下 
                {
                    if (((t%2 == 0) && (graph[xx][yy] == '-')) ||
                        ((t%2 == 1) && (graph[xx][yy] == '|')))
                    {
                        xx += dr[i][0] ;
                        yy += dr[i][1] ;
                    }
                    else continue ;
                }
                if (xx < 0 || xx >= n || yy < 0 || yy >= m) continue ;
            }
            if (graph[xx][yy] == '*') continue ;
            if (vis[xx][yy]) continue ;
            vis[xx][yy] = 1 ;
            qpush(xx, yy, t+1) ;
            qpush(xx, yy, t+2) ;
        }
    }
    return -1 ;
}


int main ()
{
    int i, j, ans ;
    while (~scanf ("%d %d%*c", &n, &m))
    {
        for (i = 0 ; i <n ; i++)
            scanf ("%s%*c", graph[i]) ;
        for(i = 0 ; i < n ; i++)
            for (j = 0 ; j < m ; j++)
            {
                if (graph[i][j] == 'S') sx = i, sy = j ;
                else if (graph[i][j] == 'T') ex = i, ey = j ;
            }
        memset (vis, 0, sizeof(vis)) ;
        qcnt = 1 ;
        ans = bfs() ;
        printf ("%d\n", ans) ;
    }
    return 0 ;
}