[LeetCode]题解（python）：048-Rotate Image

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题目来源

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https://leetcode.com/problems/rotate-image/

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

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题意分析

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Input:a matrix represented with list[list[]]

Output:a matrix 

Conditions:rotate 90 degrees clockwise

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题目思路

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注意到是将原来的矩阵顺时针旋转90度，本来直接转换比较费劲，网上大神说先转置然后每一行reverse即得所求，仔细观察矩阵的构造，的确如此，代码就几行……注意观察，不一定要一步得出答案。

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AC代码（Python）

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_author_ = "YE"
# -*- coding:utf-8 -*-

class Solution(object):
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)
        for i in range(n):
            for j in range(i + 1, n):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

        for i in range(n):
            matrix[i].reverse()

s = Solution()
f = [[1,2,3],
    [4,5,6],
    [7,8,9]]

print(s.rotate(f))
print(f)