Rotate a 2D Matrix by 90 Degrees

Program Overview

This Python program takes a 2D matrix and rotates it 90 degrees clockwise.
To achieve this, it first transposes the matrix and then reverses each row.

Python Code:

def rotate_90(matrix: list[list[int]]) -> list[list[int]]:
    # Transpose
    transposed = list(zip(*matrix))
    # Reverse each row
    rotated = [list(row)[::-1] for row in transposed]
    return rotated

def print_matrix(matrix: list[list[int]]):
    for row in matrix:
        print("  ".join(str(val) for val in row))

# Sample data
original = [
    [12, 11, 10],
    [22, 21, 20],
    [32, 31, 30],
    [42, 41, 40]
]

print("Original matrix:")
print_matrix(original)

rotated = rotate_90(original)

print("\nMatrix after 90-degree rotation:")
print_matrix(rotated)

Sample Output:

Original matrix:  
12  11  10  
22  21  20  
32  31  30  
42  41  40  

Matrix after 90-degree rotation:  
42  32  22  12  
41  31  21  11  
40  30  20  10