HDOJ_1010.Tempter of the Bone(DFS)

HDOJ_1010.Tempter of the Bone(DFS)

Problem:
From: http://acm.hdu.edu.cn/showproblem.php?pid=1010
Accept: 2009.4.14
@author fleap.
Tempter of the Bone

Problem Description

The doggie found a bone in an ancient maze, which fascinated him a lot. However, when he picked it up, the maze began to shake, and the doggie could feel the ground sinking. He realized that the bone was a trap, and he tried desperately to get out of this maze.

The maze was a rectangle with sizes N by M. There was a door in the maze. At the beginning, the door was closed and it would open at the T-th second for a short period of time (less than 1 second). Therefore the doggie had to arrive at the door on exactly the T-th second. In every second, he could move one block to one of the upper, lower, left and right neighboring blocks. Once he entered a block, the ground of this block would start to sink and disappear in the next second. He could not stay at one block for more than one second, nor could he move into a visited block. Can the poor doggie survive? Please help him.

 

Input

The input consists of multiple test cases. The first line of each test case contains three integers N, M, and T (1 < N, M < 7; 0 < T < 50), which denote the sizes of the maze and the time at which the door will open, respectively. The next N lines give the maze layout, with each line containing M characters. A character is one of the following:

'X': a block of wall, which the doggie cannot enter;
'S': the start point of the doggie;
'D': the Door; or
'.': an empty block.

The input is terminated with three 0's. This test case is not to be processed.

 

Output

For each test case, print in one line "YES" if the doggie can survive, or "NO" otherwise.

 

Sample Input

4 4 5
S.X.
..X.
..XD
....
3 4 5
S.X.
..X.
...D
0 0 0

 

Sample Output

NO
YES

 1 //   DFS
 2 #include < iostream >
 3 using   namespace  std;
 4 //  Global variables
 5 char  maze[ 9 ][ 9 ];
 6 int  x, y , n, desx, desy,temp;  //  x is row y is cow n is steps
 7 bool  escape;  // run or not
 8 int  d[ 4 ][ 2 ]  =   {{0, 1},{0, -1},{1, 0},{-1, 0}} ;  //  stand for four directions
 9
10 void  DFS( int  stax,  int  stay,  int  step)  {
11    if( stax > x || stay > y ||
12       stay <= 0 || stax <= 0 )
13    return;
14    if( stax == desx && stay == desy && step == n){
15    escape = true;
16    return;
17    }
18    if(escape) return;
19    // cut tree
20    temp = n - step - abs(stax - desx) - abs(stay - desy);
21    if(temp < 0 || temp & 1) return;
22    for(int i = 0; i < 4; i++) {
23        if(maze[stax + d[i][0]][stay + d[i][1]] != 'X'){
24        maze[stax + d[i][0]][stay + d[i][1]] = 'X';
25        DFS(stax + d[i][0], stay + d[i][1], step + 1);
26        maze[stax + d[i][0]][stay + d[i][1]] = '.';  // back
27        }
28    }
29    return;
30}
31
32 int  main()  {
33    int stax, stay;
34    while(cin >> x >> y >> n  && x + y + n) {
35        escape = false; int wall = 0;
36        for(int i = 1; i <= x; i++) {
37            for(int j = 1; j <= y; j++) {
38                cin >> maze[i][j];
39                if(maze[i][j] == 'S') {
40                stax = i;
41                stay = j;
42                }
43                if(maze[i][j] == 'D') {
44                desx = i;
45                desy = j;
46                }
47                if(maze[i][j] == 'X'){
48                wall++;
49                }
50            }
51        }
52        if( x * y - wall <= n ) {
53            cout << "NO\n";
54            continue;
55        }
56        maze[stax][stay] = 'X';
57        DFS(stax, stay, 0);
58        cout << ( escape ? "YES" : "NO" ) << endl;
59    }
60    return 0;
61}