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;

}