Tempter of the Bone

Tempter of the Bone

 

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

 注释：深度优先搜索 dfs

 

package test_jgraph;

import java.util.Iterator;

import junit.framework.TestCase;

public classTestDfs extendsTestCase {

    public void testDfs() {

        new Maze().doTest();

    }

    public class Maze {

        public void doTest() {

            MazeTestCasets1= newMazeTestCase(4, 4, 5);

            ts1.setData("S.X...X...XD....");

            ts1.initStart();

            assertTrue(dfs(ts1.getStart()[0], ts1.getStart()[1], 0, ts1) == false);

            ts1.prettyPrint();

 

            MazeTestCasets2= newMazeTestCase(3, 4, 5);

            ts2.setData("S.X...X....D");

            ts2.initStart();

            assertTrue(dfs(ts2.getStart()[0], ts2.getStart()[1], 0, ts2) == true);

            ts2.prettyPrint();

        }

 

        public boolean dfs(intn, int m, int t, MazeTestCase ts) {

            if (ts.isOutOfBoundary(n, m, t)) {

                return false;

            }

            if (ts.isFind(n, m, t)) {

                return true;

            }

            TraverseIterator<int[]> iterator = iterator();

            while (iterator.hasNext()) {

 

                int dir[] = iterator.next();

 

                int n1 = n + dir[0];

                int m1 = m + dir[1];

                if (!ts.isOutOfBoundary(n1, m1, t + 1)) {

 

                    Stringc = ts.getValue(n1, m1);

                    if (ts.isValid(c)) {

                        ts.setValue(n1, m1, "O" + (t + 1));

                        if (dfs(n1, m1, t + 1, ts)) {

                            return true;

                        }

                        ts.setValue(n1, m1, ".");

                    }

                }

            }

            return false;

        }

        private TraverseIterator<int[]> iterator() {

            return new TraverseIterator<int[]>();

        }

    }

    class MazeTestCase {

        private int N;

        private int M;

        private int T;

        private String[][] data;
 

        private int[] door;

        private int[] start;

 

        public MazeTestCase(int n, int m, int t) {

            N = n;

            M = m;

            T = t;

        }

 

        public boolean isValid(String c) {

            return !c.equals("X") && !c.startsWith("O");

        }

 

        public void initStart() {

            setValue(getStart()[0],getStart()[1], "O");

        }

 

        public void setData(String str) {

 

            data = new String[N][M];

 

            for (int i = 0; i < N; i++) {

                for (int j = 0; j < M; j++) {

                    data[i][j] = String.valueOf(str.charAt(i * M + j));

                    if (data[i][j].equals("S")) {

                        start = new int[] { i, j };

                    }

 

                    if (data[i][j].equals("D")) {

                        door = new int[] { i, j };

                    }

                }

            }

        }

 

        public void setValue(int n, int m, String c) {

            data[n][m] = c;

        }

 

        public String getValue(int n, int m) {

            return data[n][m];

        }

 

        private int[] getDoor() {

            return door;

        }

 

        private int[] getStart() {

            return start;

        }

 

        public boolean isOutOfBoundary(int n, int m, int t) {

            return n < 0 || n >= N || m < 0 || m >= M || t < 0 || t > T;

        }

 

        public boolean isFind(int n, int m, int t) {

            return n == getDoor()[0] && m == getDoor()[1] && t == T;

        }

       

        public void prettyPrint(){

            for( int i= 0 ; i < N; i ++){

                for( int j = 0 ; j < M; j ++){

                    System.out.print("\t" + data[i][j] + "\t");

                }

                System.out.println();

            }

            System.out.println();

        }

    }

 

    class TraverseIterator<T> implements Iterator<T> {

 

        final int[][] dirList = { { 0, 1 }, { 1, 0 },{ 0, -1 }, { -1, 0 } };

 

        int count = 0;

 

        @Override

        public boolean hasNext() {

 

            return count < 4;

        }

 

        @SuppressWarnings("unchecked")

        @Override

        public T next() {

            return (T) dirList[count++];

        }

 

        @Override

        public void remove() {

        }

 

    }

 

}