Spiral Matrix

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
For example,
Given the following matrix:

[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

You should return [1,2,3,6,9,8,7,4,5].

Naive Way: In order to traversal the matrix in spiral order, I need to keep two lengths, one is the current length of row that need to be traversal, one is the current length of column that need to be traversal. Also use a variable to control direction. Like 0-> going left, 1-> going down, 2-> going right, 3-> going up.

 public class Solution {  
   public List<Integer> spiralOrder(int[][] matrix) {  
     List<Integer> rslt = new ArrayList<Integer>();  
     if(matrix.length==0) return rslt;  
     int rowLen = matrix[0].length, colLen = matrix.length-1;  
     int x = 0, y = -1;  
     int dir = 0;  
     while(rowLen >= 0 && colLen >= 0){  
       switch(dir){  
         case 0:  
           for(int i = 0;i < rowLen;i++) rslt.add(matrix[x][++y]);  
           rowLen--;  
           break;  
         case 1:  
           for(int i = 0;i < colLen;i++) rslt.add(matrix[++x][y]);  
           colLen--;  
           break;  
         case 2:  
           for(int i = 0;i < rowLen;i++) rslt.add(matrix[x][--y]);  
           rowLen--;  
           break;  
         case 3:  
           for(int i = 0;i < colLen;i++) rslt.add(matrix[--x][y]);  
           colLen--;  
           break;  
       }  
       dir = ++dir%4;  
     }  
     return rslt;  
   }  
 }