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].

public class Solution {
	List<Integer>  list = new ArrayList<>();
    public List<Integer> spiralOrder(int[][] matrix) {
    	help(matrix);
    	return list;
    }
    private void  help (int [][]matrix){
    	if(matrix.length==0) return;
    	int row = matrix.length;
    	int column = matrix[0].length;
    	if(row == 1){
    		for(int i=0;i<column;i++) list.add(matrix[0][i]);
    	}else if(column == 1){
    		for(int i=0;i<row;i++) list.add(matrix[i][0]);
    	}else{
			for (int i = 0; i < column - 1; i++) list.add(matrix[0][i]);
			for (int i = 0; i < row - 1; i++) list.add(matrix[i][column - 1]);
			for (int i = column - 1; i > 0; i--)list.add(matrix[row - 1][i]);
			for (int i = row - 1; i > 0; i--)list.add(matrix[i][0]);
    	}
    	if(row-2<=0||column-2<=0) return;
    	int [][]matrix2 = new int[row-2][column-2];
    	for(int i =0,j=1;i<row-2;i++,j++) matrix2[i] = Arrays.copyOfRange(matrix[j],1, column-1);
    	help(matrix2);
    }
}

[LeetCode]Spiral Matrix