59. Spiral Matrix II

2019-05-09

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:

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

Code:

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