hdoj1312Red and Black

Red and Black

[align=left]Problem Description[/align]
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.

[align=left]Input[/align]
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)

[align=left]Output[/align]
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).

[align=left]Sample Input[/align]

6 9
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0

[align=left]Sample Output[/align]

45
59
6
13
代码：
#include<stdio.h>
#include<string.h>
char map[1010][1010];
int vis[1010][1010],n,m,ans,sx,sy;
void dfs(int x,int y)
{
if(x<0||x>=m||y<0||y>=n||vis[x][y]||map[x][y]=='#')
return ;
vis[x][y]=1;
ans++;
dfs(x+1,y);
dfs(x,y+1);
dfs(x-1,y);
dfs(x,y-1);
}
int main()
{
while(scanf("%d%d",&n,&m)&&n||m)
{
ans=0;
memset(vis,0,sizeof(vis));
memset(map,0,sizeof(map));
for(int i=0;i<m;i++)
{
scanf("%s",&map[i]);

for(int j=0;j<n;j++)
{
if(map[i][j]=='@')
sx=i,sy=j;
}
}
dfs(sx,sy);
printf("%d\n",ans);
}
return 0;
}

思路：深搜，dfs，这是第一次接触深搜题，乍一看一点思路也没有啊，然后学长讲完之后也是晕头转向的，迷迷糊糊，晕。然后自己照着代码敲了几遍，记住代码，再根据代码慢慢看懂了，memset(vis,0,sizeof(vis)); memset(map,0,sizeof(map));这个是要记住的，就是把所有的行行竖竖清零，在dfs，bfs里经常用到。然后就是定义dfs了，要记住确定方向dfs(x+1,y);dfs(x,y+1);dfs(x-1,y);dfs(x,y-1);，分别代表上下左右，其次就是找原始的点，然后本题就ac啦，注意不会多多敲几遍哈！！