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Rotate Image

Problem Statement​

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Leetcode link

Example 1:​

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]

Example 2:​

Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]

Constraints:​

  • n == matrix.length == matrix[i].length
  • 1 <= n <= 20
  • -1000 <= matrix[i][j] <= 1000

Code​

Python Code
class Solution(object):
    def rotate(self, matrix):
        n=len(matrix)
        for i in range(int(n/2)):
            for j in range(i,n-i-1):
                matrix[i][j],matrix[j][n-i-1],matrix[n-i-1][n-j-1],matrix[n-j-1][i]=matrix[n-j-1][i], matrix[i][j],matrix[j][n-i-1],matrix[n-i-1][n-j-1]