POJ 1979 Red and Black （DFS）

POJ 1979 Red and Black （DFS）2014-07-24Time Limit: 1000MS

Memory Limit: 30000K

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

Source

Japan 2004 Domestic

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完整代码：

/*16ms,388KB*/#include<cstdio>#include<cstring>char grid[25][25];bool vis[25][25];int cnt, x, y;void dfs（int i, int j）{if （grid[i][j] == "#" || vis[i][j]） return;vis[i][j] = true;++cnt;dfs（i - 1, j）; dfs（i + 1, j）; dfs（i, j - 1）; dfs（i, j + 1）;}int main（）{int i, j, xx, yy;while （scanf（"%d%d
", &x, &y）, x）{memset（grid, "#", sizeof（grid））;for （i = 1; i <= y; ++i）{for （j = 1; j <= x; ++j）{grid[i][j] = getchar（）;if （grid[i][j] == "@"）xx = i, yy = j;}getchar（）;}memset（vis, 0, sizeof（vis））;cnt = 0;dfs（xx, yy）;printf（"%d
", cnt）;}return 0;}

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