62 leetcode - Spiral Matrix II

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于 2016-12-26 18:19:15 发布

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本文介绍了一个使用Python实现的螺旋矩阵生成算法。该算法接收一个整数n作为输入，并生成一个n×n的矩阵，矩阵中的元素按螺旋顺序从1到n²填充。文章通过实例展示了如何为不同大小的矩阵生成相应的螺旋填充。

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#!/usr/bin/python
# -*- coding: utf-8 -*-
'''
Spiral Matrix II
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 ]
]
'''
class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        if n == 0:
            return []
        matrix = [[None] * n for i in range(n)]
        up = left = 0
        down = right = n - 1
        nums = 1
        while down >= up and left <= right:
            col = left
            while col <= right:
                matrix[up][col] = nums
                nums += 1
                col += 1
            up += 1

            row = up
            while row <= down:
                matrix[row][right] = nums
                nums += 1
                row += 1
            right -= 1

            col = right
            while col >= left:
                matrix[down][col] = nums
                nums += 1
                col -= 1
            down -= 1

            row = down
            while row >= up:
                matrix[row][left] = nums
                nums += 1
                row -= 1
            left += 1

        return matrix



if __name__ == "__main__":
    s = Solution()
    print s.generateMatrix(1)
    print s.generateMatrix(2)
    print s.generateMatrix(3)
    print s.generateMatrix(4)