HDU ACM 1312 ：DFS解决

迷宫问题和求总数问题

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)

 

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

     题目虽然是英文的，但还是比较的简单。大体意思就是说，一个人被困在迷宫里，只能走点线！问最多能够走多少步。

     这种问题用双循环判断是否是“.”，来找。是不现实的！所以这里要用到DFS。

　 简单来说DFS就是像水波一样，遇到障碍就结束。再在其中加入其它的作用来实现迷宫之类的问题。

   

empty
#include              /*qsort 函数的用法    快速排序*/
#include 
#include 
using namespace std;
int compare(const void *p1,const void *p2) 
{
    int *pt1=(int*)p1;                     
    int *pt2=(int*)p2;
    return *pt1-*pt2;                     
int main()
{
    int a[10]={1,5,2,6,9,8,41,56,9,6};
    qsort(a,10,sizeof(int ),compare);   
    for(int i=0;i<10;i++)
    {
        cout <