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].

Java

public class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> rst = new ArrayList<Integer>();
        if(matrix.length < 1) {
            return rst;
        }

        int row = matrix.length;
        int col = matrix[0].length;
        int x = 0, y = 0;

        while(row > 0 && col > 0) {
            if(row == 1) {
                for(int i = 0; i < col; i++) {
                    rst.add(matrix[x][y++]);
                }
                break;
            }
            if(col == 1) {
                for(int i = 0; i < row; i++) {
                    rst.add(matrix[x++][y]);
                }
                break;
            }

            for(int i = 0; i < col - 1; i++) {
                rst.add(matrix[x][y++]);
            }
            for(int i = 0; i < row - 1; i++) {
                rst.add(matrix[x++][y]);
            }
            for(int i = 0; i < col - 1; i++) {
                rst.add(matrix[x][y--]);
            }
            for(int i = 0; i < row - 1; i++) {
                rst.add(matrix[x--][y]);
            }
            x++;
            y++;
            row -= 2;
            col -= 2;
        }
        return rst;
    }
}