打印蛇形排列的数（这算法挺牛的）

1. class  snakePrint {  
2.     static   int  length =  7 ;  
3.     static   int  value =  1 ;  
4.     static   int [][] snake =  new   int [length][length];  
5.     static  Direction lastDirection = Direction.Right;  
6.   
7.     static   enum  Direction {  
8.         Right, Down, Left, Up;  
9.     }  
10.   
11.     public   static   void  initialArray() {  
12.         int  row =  0 , line =  0 ;  
13.         for  ( int  c =  0 ; c < length * length; c++) {  
14.             snake[row][line] = value;  
15.             lastDirection = findDirection(row, line);  
16.             switch  (lastDirection) {  
17.                 case  Right:  
18.                     line++;  
19.                     break ;  
20.                 case  Down:  
21.                     row++;  
22.                     break ;  
23.                 case  Left:  
24.                     line--;  
25.                     break ;  
26.                 case  Up:  
27.                     row--;  
28.                     break ;  
29.                 default :  
30.                     System.out.println("error" );  
31.             }  
32.             value++;  
33.         }  
34.     }  
35.   
36.     static  Direction findDirection( int  row,  int  line) {  
37.         Direction direction = lastDirection;  
38.         switch  (direction) {  
39.             case  Right: {  
40.                 if  ((line == length -  1 ) || (snake[row][line +  1 ] !=  0 ))  
41.                     direction = direction.Down;  
42.                 break ;  
43.             }  
44.             case  Down: {  
45.                 if  ((row == length -  1 ) || (snake[row +  1 ][line] !=  0 ))  
46.                     direction = direction.Left;  
47.                 break ;  
48.             }  
49.             case  Left: {  
50.                 if  ((line ==  0 ) || (snake[row][line -  1 ] !=  0 ))  
51.                     direction = direction.Up;  
52.                 break ;  
53.             }  
54.             case  Up: {  
55.                 if  (snake[row -  1 ][line] !=  0 )  
56.                     direction = direction.Right;  
57.                 break ;  
58.             }  
59.         }  
60.         return  direction;  
61.     }  
62.   
63.     public   static   void  main(String[] args) {  
64.         initialArray();  
65.   
66.         // display.....   
67.         for  ( int  i =  0 ; i < length; i++) {  
68.             for  ( int  j =  0 ; j < length; j++) {  
69.                 System.out.print(snake[i][j] + "  " );  
70.             }  
71.             System.out.println();  
72.         }  
73.     }  
74. }