Q: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.
#include<iostream>
#include <stdlib.h>
#define MAX_NUM 21
using namespace std;
int dire[4][2] = { {1, 0}, {-1, 0}, {0, 1}, {0, -1} }; //分别定义四个方向
int DFS(char arr[][MAX_NUM], int start_x, int start_y, int H, int W) {
if (arr[start_x][start_y] == '#'|| start_x >= W || start_y >= H || start_x < 0 || start_y < 0) //退出条件
{
return 0;
}
int res = 1;
arr[start_x][start_y] = '#'; //遍历以后进行标记，防止重复计数
for (int i = 0; i < 4; i++)
{
res += DFS(arr, start_x + dire[i][0], start_y + dire[i][1], H, W);
}
return res;
}
int main()
{
char arr[MAX_NUM][MAX_NUM];
memset(arr, 0, sizeof(arr));
int H, W, start_x, start_y;
while (cin >> H >> W&&(H != 0&&W != 0)) {
for (int i = 0; i < W; i++)
{
for (int j = 0; j < H; j++)
{
cin >> arr[i][j];
if (arr[i][j] == '@')
{
start_x = i;
start_y = j;
}
}
}
int res = DFS(arr, start_x, start_y, H, W);
cout << res << endl;
}
return 0;
}
