Spiral Matrix II

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example, Given n = 3,

You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]

URL: https://leetcode.com/problems/spiral-matrix-ii/

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        if n == 0:
            return []
        elif n == 1:
            return [[1]]
        else:
            #no of rows
            r = n
            #no of columns
            c = n
            #start of row
            k = 0
            #start of column
            l = 0

            #allocate a square matrix with all zeros
            matrix = [[0 for j in range(c)] for i in range(r)]
            #counter for the elements
            count = 1

            while k < r and l < c:
                #fill the first row
                for i in range(l, c):
                    matrix[k][i] = count
                    count += 1

                k += 1

                #fill the last column
                for i in range(k, r):
                    matrix[i][c-1] = count
                    count += 1

                c -= 1

                #fill the last row
                if k < r:
                    for i in range(c-1, l-1, -1):
                        matrix[r-1][i] = count
                        count += 1
                    r -= 1

                #fill the first column
                if l < c:
                    for i in range(r-1, k-1, -1):
                        matrix[i][l] = count
                        count += 1
                    l += 1

            return matrix