POJ 1979 && HDU 1312 Red and Black(DFS)

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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
#include <iostream>#include <cstdio>using namespace std;char map[25][25];int num;int w,l;//w->width l->lenthint dx[4] ={0,0,1,-1};int dy[4] ={1,-1,0,0};void dfs(int x,int y){    int i,xx,yy;    for(i=0;i<4;i++)    {        xx = x+dx[i];        yy = y+dy[i];        if(xx>=0 && xx<w && yy>=0 && yy<l && map[xx][yy]=='.')        {            num++;            map[xx][yy] = '@';            dfs(xx,yy);        }    }}int main(){    //freopen("test.txt","r",stdin);    int i,j;    int sx,sy;    while(cin>>l>>w && l)    {        for(i=0;i<w;i++)        {            for(j=0;j<l;j++)            {                cin>>map[i][j];                if(map[i][j]=='@')                {                    sx = i;                    sy = j;                }//            }        }        map[sx][sy] = '#';        num = 1;        dfs(sx,sy);        cout << num << endl;    }    //cout << "Hello world!" << endl;    return 0;}

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