LeetCode/059. Spiral Matrix II at master · muweid/LeetCode · GitHub

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#!/usr/bin/env python3

__author__ = 'Wei Mu'

class Solution:
    def generateMatrix(self, n: 'int') -> 'List[List[int]]':

        if n == 0:
            return([])

        global ans
        ans = []

        for i in range(n):
            ans.append([None] * n)

        start_num = 1
        row_num = 0

        while row_num <= n//2:
            start_num, row_num = self.fill_spiral(start_num, row_num, n)

        return ans

    def fill_spiral(self, start_num, row_num, n):
        global ans

        if n % 2 == 1 and row_num == n//2:
            ans[row_num][row_num] = start_num
            return(start_num+1, row_num+1)

        for i in range(row_num, n-row_num-1):
            ans[row_num][i] = start_num
            start_num += 1
        for i in range(row_num, n-row_num-1):
            ans[i][n-1-row_num] = start_num
            start_num += 1
        for i in range(n-1-row_num, row_num, -1):
            ans[n-1-row_num][i] = start_num
            start_num += 1
        for i in range(n-1-row_num, row_num, -1):
            ans[i][row_num] = start_num
            start_num += 1

        return(start_num, row_num+1)