[Solved] 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.

Question

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.

Example 1:

mat1
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]

Example 2:

mat2
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

Python Solution

class Solution:
    def rotate(self, matrix):
        """
        Do not return anything, modify matrix in-place instead.
        """
        l = len(matrix)
        if l==1 or l==0:
            return
        for i in range(l//2):
            for j in range(i,l-1):
                matrix[i][j],matrix[j][l-1] = matrix[j][l-1], matrix[i][j]
                matrix[i][j],matrix[l-1][l-1-j+i] = matrix[l-1][l-1-j+i], matrix[i][j]
                matrix[i][j],matrix[l-1-j+i][i] = matrix[l-1-j+i][i], matrix[i][j]
            l-=1
        return
        
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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