zoj 2165 Red and Black （DFs）poj 1979

Red and Black

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Time Limit: 2 Seconds      Memory Limit: 65536 KB

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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

dfs练习题 求与 @可走的.个数 本身也算

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define N 22
int dir[4][2]={-1,0,1,0,0,-1,0,1};
char map[N][N];
int cnt;
int h,w;
bool ok(int x,int y)
{
    if(x<0||x>=h) return false;
    if(y<0||y>=w) return false;
    if(map[x][y]=='#') return false;
    return true;
}
void dfs(int a,int b)
{
    cnt++;
    map[a][b]='#';
    int i;
    int x,y;
    for(i=0;i<4;i++)
    {
        x=a+dir[i][0];
        y=b+dir[i][1];
        if(ok(x,y))
        {
            dfs(x,y);
        }
    }
}
int main()
{

    int i,j;
    int s,t;
    while(scanf("%d %d",&w,&h),h||w)
    {
         getchar();
        for(i=0;i<h;getchar(),i++)
         for(j=0;j<w;j++)
         {
             scanf("%c",&map[i][j]);
             if(map[i][j]=='@') s=i,t=j;
         }
        cnt=0;
        dfs(s,t);
        printf("%d\n",cnt);
    }
    return 0;
}