poj 1979 Red and Black

Description

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)
The end of the input is indicated by a line consisting of two zeros.

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

4559613简单搜索 直接dfs即可。
#include<stdio.h>#include <iostream>#include<string.h>#include <algorithm>using namespace std;int vis[25][25];char map[25][25];int w,h,sum;int xx,yy;int dx[]={1,0,-1,0};int dy[]={0,1,0,-1};void dfs(int x,int y){    for(int i=0;i<4;i++)        {            int x1=x+dx[i];            int y1=y+dy[i];            if(map[x1][y1]=='#')continue;//红色            if((x1<0||x1>=h)||(y1<0||y1>=w))continue;//出界            if(!vis[x1][y1])//标记过            {                vis[x1][y1]=1;                sum++;                dfs(x1,y1);            }        }}int main(){    while(scanf("%d%d",&w,&h))    {        if(w==0&&h==0)            break;        memset(vis,0,sizeof(vis));        sum=0;        for(int i=0;i<h;i++)        {            scanf("%s",&map[i]);            for(int j=0;j<w;j++)                if(map[i][j]=='@')                {                    xx=i;yy=j;                }        }        dfs(xx,yy);        if(sum)            cout<<sum<<endl;            else                cout<<1<<endl;    }}