Leetcode: Spiral Matrix II

Question

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 ]
]
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Hide Similar Problems (M) Spiral Matrix

Solution

class Solution(object):
    def generateMatrix(self, n):
        """ :type n: int :rtype: List[List[int]] """

        if n==0:
            return []

        total = n**2
        res = [[0]*n for dummy in range(n)]
        levelnum = n / 2

        i = 1
        for level in range(levelnum):
            for ind in range(level, n-level-1):
                res[level][ind] = i
                i += 1

            for ind in range(level, n-level-1):
                res[ind][n-1-level] = i
                i += 1

            for ind in range(n-1-level, level, -1):
                res[n-1-level][ind] = i
                i += 1

            for ind in range(n-1-level, level, -1):
                res[ind][level] = i
                i += 1

        if n%2==1:
                res[n/2][n/2] = i

        return res