public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<Integer>();
        if (matrix.length == 0) {
			return result;
		}
        int beginX = 0, endX = matrix[0].length - 1;//水平方向
        int beginY = 0, endY = matrix.length - 1;//垂直方向
        
        while(true){
        	//从左向右
        	for (int i = beginX; i <= endX; ++i) {
				result.add(matrix[beginY][i]);
			}
        	if(++beginY > endY) break;
        	
        	//从上到下
        	for (int i = beginY; i <= endY; ++i) {
        		result.add(matrix[i][endX]);
			}
        	if(beginX > -- endX) break;
        	
        	//从右到左
        	for (int i = endX; i >= beginX; --i) {
        		result.add(matrix[endY][i]);
			}
        	
        	if(beginY > --endY) break;
        	
        	//从下到上
        	for (int i = endY; i >= beginY; --i) {
        		result.add(matrix[i][beginX]);
			}
        	
        	if(++beginX > endX) break;
        }
        return result;
    }
}