原題鏈接 Red and Black Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 33776 Accepted: 18319 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

45 59 6 13 Source

Japan 2004 Domestic 題意：有一個矩形的房間，里面鋪滿了方形的瓷磚。每一個瓷磚有紅色還有黑色兩種，人只能站在黑色的瓷磚上不能站在紅色的瓷磚上，每次只能走前后左右四個方向的四個瓷磚，計算能夠到達的黑色瓷磚的總面積數。 思路：深度優先搜索，走過的地方直接變成紅色