順時針打印矩陣

• 輸入一個矩陣，按照從外向裏以順時針的順序依次打印出每個數字，例如，若是輸入以下矩陣： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 則依次打印出數字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.
• 注意一些細節便可，代碼以下：

import java.util.ArrayList;
import java.util.List;
public class Solution {
	public ArrayList<Integer> printMatrix(int[][] matrix) {
		ArrayList<Integer> list = new ArrayList<Integer>();
		if (matrix.length == 0 && matrix[0].length == 0)
			return list;
		int direction[][] = new int[][] { { 0, 1 }, { 1, 0 }, { 0, -1 },
				{ -1, 0 } };
		int mark[][] = new int[matrix.length][matrix[0].length];
		printMatrixRecur(matrix, mark, 0, direction, 0, 0, list);
		return list;
	}	
    void printMatrixRecur(int[][] matrix, int[][] mark, int dirct,int[][] direction, int x, int y, List<Integer> list) {
		if (mark[x][y] == 0) {
			list.add(matrix[x][y]);
			mark[x][y] = 1;
		}
		for (int i = 0; i < 4; ++i) {
			int j = (dirct + i) % 4;
			int dx = x + direction[j][0];
			int dy = y + direction[j][1];
			if (dx >= 0 && dx < matrix.length && dy >= 0
					&& dy < matrix[0].length && mark[dx][dy] == 0)
				printMatrixRecur(matrix, mark, j, direction, dx, dy, list); //direc在下一次遞歸中直接加上1標識下一個方向
		}
	}
}