【LeetCode with Python】 59. Spiral Matrix II

题目

原题页面:https://oj.leetcode.com/problems/spiral-matrix-ii/
本文地址:http://leetcode.xnerv.wang/spiral-matrix-ii/
题目类型:Array
难度评价:Medium
类似题目:(M) Spiral Matrix

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:
<br/> [<br/> [ 1, 2, 3 ],<br/> [ 8, 9, 4 ],<br/> [ 7, 6, 5 ]<br/> ]<br/>


分析

(M) Spiral Matrix类似,使用两重for循环,但不是输出螺旋状遍历的元素,而是螺旋状地将元素填入到二维数组中。


代码

class Solution:
    # @return a list of lists of integer
    def generateMatrix(self, n):

        if 0 == n:
            return [ ]
        m = n
        index = 1
        matrix = [[0 for x in range(0, n)] for y in range(0, n)]
        round = (n + 1) / 2
        for x in range(0, round):
            for y in range(x, n - x):
                matrix[x][y] = index
                index += 1
            for y in range(x + 1, m - x - 1):
                matrix[y][n - x - 1] = index
                index += 1
            if m - 2 * x > 1:  ###
                for y in range(n - x - 1, x - 1, -1):
                    matrix[m - x - 1][y] = index
                    index += 1
            if n - 2 * x > 1:      ###
                for y in range(m - x - 2, x, -1):   ###
                    matrix[y][x] = index
                    index += 1
        return matrix

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