59. Spiral Matrix II

Given a positive integer n, generate a square matrix filled with elements from 1 to _n_2 in spiral order.

Example:

Input: 3
Output:
[
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
]

Code:

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        A, lo = [], n*n+1
        while lo > 1:
            lo, hi = lo - len(A), lo
            A = [range(lo, hi)] + zip(*A[::-1])
        return A

 ||  =>  |9|  =>  |8|      |6 7|      |4 5|      |1 2 3|
                  |9|  =>  |9 8|  =>  |9 6|  =>  |8 9 4|
                                      |8 7|      |7 6 5|