Problem 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.<br><br>Write
a program to count the number of black tiles which he can reach by repeating the moves described above. <br>
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.<br><br>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.<br><br>'.' - a black tile <br>'#' - a red tile <br>'@' - a man on a black tile(appears exactly once in a data set) <br>
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). <br>
Sample Input
6 9<br>....#.<br>.....#<br>......<br>......<br>......<br>......<br>......<br>#@...#<br>.#..#.<br>11 9<br>.#.........<br>.#.#######.<br>.#.#.....#.<br>.#.#.###.#.<br>.#.#..@#.#.<br>.#.#####.#.<br>.#.......#.<br>.#########.<br>...........<br>11 6<br>..#..#..#..<br>..#..#..#..<br>..#..#..###<br>..#..#..#@.<br>..#..#..#..<br>..#..#..#..<br>7 7<br>..#.#..<br>..#.#..<br>###.###<br>...@...<br>###.###<br>..#.#..<br>..#.#..<br>0 0<br>
Sample Output
45<br>59<br>6<br>13<br>
題意：有紅、黑兩種顏色，只能走黑色，上、下、左、右走。求走過的黑色的。
思路：dfs，注意走過的地方。
代碼：
#include <iostream>
#include<stdlib.h>
#include<string.h>
#include<fstream>
using namespace std;
char a[25][25];
int flag[25][25];
int sum;
void DFS(int x,int y)
{
if(a[x-1][y]=='.' && flag[x-1][y]==0)
{
sum++;
flag[x-1][y]=1;
DFS(x-1,y);
}
if(a[x][y-1]=='.' && flag[x][y-1]==0)
{
sum++;
flag[x][y-1]=1;
DFS(x,y-1);
}
if(a[x][y+1]=='.' && flag[x][y+1]==0)
{
sum++;
flag[x][y+1]=1;
DFS(x,y+1);
}
if(a[x+1][y]=='.' && flag[x+1][y]==0)
{
sum++;
flag[x+1][y]=1;
DFS(x+1,y);
}
}
int main()
{
freopen ("C:\\Users\\liuzhen\\Desktop\\11.txt", "r", stdin);
int n,m,i,j;
while(cin>>m>>n)
{
if(m==0&&n==0)
break;
sum=0;
memset(flag,0,sizeof(flag));
memset(a,'#',sizeof(a));
for(i=1;i<=n;i++)
{
for(j=1;j<=m;j++)
{
cin>>a[i][j];
}
}
for(i=1;i<=n;i++)
{
for(j=1;j<=m;j++)
{
if(a[i][j]=='@')
{
sum++;
flag[i][j]=1;
DFS(i,j);
i=n;
j=m;
}
}
}
cout<<sum<<endl;
}
freopen ("con", "r", stdin);
system("pause");
return 0;
}
