HDU1312迷宫问题

问题描述：
There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can’t move on red tiles, he can move only on black tiles.

Write a program to count the number of black tiles which he can reach by repeating the moves described above.
Input
The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.

There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.

‘.’ - a black tile
‘#’ - a red tile
‘@’ - a man on a black tile(appears exactly once in a data set)
Output
For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).
Sample Input
6 9
….#.
…..#
……
……
……
……
……
#@…#
.#..#.
11 9
.#………
.#.#######.
.#.#…..#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#…….#.
.#########.
………..
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
…@…
###.###
..#.#..
..#.#..
0 0
Sample Output
45
59
6
13

AC代码：

#include<stdio.h>#include<string.h>char mp[25][25];int book[25][25],sum,n,m;struct node{    int x,y;} Q[410];void bfs(int x,int y){    int nx[4][2]={{0,-1},{1,0},{0,1},{-1,0}};    int head=1,tail=2;    Q[head].x=x;    Q[head].y=y;    while(head<tail)    {        for(int i=0;i<4;i++)        {            int tx=Q[head].x+nx[i][0];            int ty=Q[head].y+nx[i][1];            if(tx<0||ty<0||tx>=n||ty>=m) continue;            if(book[tx][ty]==0&&mp[tx][ty]=='.')            {                Q[tail].x=tx;                Q[tail].y=ty;                book[tx][ty]=1;                sum++;                tail++;            }        }        head++;    }    return;}int main(){    while(~scanf("%d %d",&m,&n)&&m+n)    {        getchar();        int i,j,sx,sy;        memset(book,0,sizeof(book));        for(i=0;i<n;i++)        {            scanf("%s",mp[i]);            for(j=0;j<m;j++)            {                if(mp[i][j]=='@')                {                    sum=1;                    book[i][j]=1;                    sx=i;                    sy=j;                }            }        }        bfs(sx,sy);        printf("%d\n",sum);    }    return 0;}

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