POTD #1 Rotate by 90 degree - Matrix Anticlockwise | Geeks For Geeks

After a long time, i tried competitive programming. Seems i need to do it more. This is a geeks for geeks POTD (Problem of the day) problem.

Link: https://www.geeksforgeeks.org/problems/rotate-by-90-degree-1587115621/1

Given a square matrix mat[][] of size n x n. The task is to rotate it by 90 degrees in an anti-clockwise direction without using any extra space. 

Input:

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

Input: mat[][] = [[1, 2],
                [3, 4]]
Output: Rotated Matrix:
[2, 4]
[1, 3]

Solution

I tried to reverse the each row and found the transpose of the matrix. Since i am aware of transpose , i directly went to this approach.

#User function Template for python3


class Solution:
    
    #Function to rotate matrix anticlockwise by 90 degrees.
    def rotateby90(self, mat): 
        # code here
        n = len(mat)
            
        # reversing
        for row in mat:
            i = 0
            j = len(row) - 1
            while i  < j:
                row[i], row[j] = row[j], row[i]
                i += 1
                j -= 1
                
                
    
        # Performing Transpose
        for i in range(n):
            for j in range(i + 1, n):
                mat[i][j], mat[j][i] = mat[j][i], mat[i][j]