Python Program for Mirror of matrix across diagonal

The mirror of a matrix across a diagonal means swapping the elements at position[i, j] with the elements at position[j, i]. This operation is also known as finding the transpose of a matrix.

Problem Statement

You are given a 2-D matrix in Python in the form of a nested list, and you need to find the transpose, that is, the mirror of that matrix across the diagonal.

Example

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

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

Method 1: Using Nested for Loop

In this approach, we will use the nested for loop to find the mirror of the matrix across a diagonal ?

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

print("Original Matrix")
for row in matrix:
    print(row)

# Create new nested list to store mirror matrix
mirror_matrix = [[0 for i in range(len(matrix))] for j in range(len(matrix[0]))]

# Nested for loop to iterate through lists
for i in range(len(matrix)):
    for j in range(len(matrix[0])):
        mirror_matrix[j][i] = matrix[i][j]

print("\nMirror Matrix")
for row in mirror_matrix:
    print(row)

Original Matrix
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]

Mirror Matrix
[1, 4, 7]
[2, 5, 8]
[3, 6, 9]

Method 2: Using List Comprehension

In this approach, we will use the concept of list comprehension to find the mirror of the matrix across a diagonal ?

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

print("Original Matrix")
for row in matrix:
    print(row)

# Mirror matrix using list comprehension
mirror_matrix = [
    [matrix[i][j] for i in range(len(matrix))] for j in range(len(matrix[0]))
]

print("\nMirror Matrix")
for row in mirror_matrix:
    print(row)

Original Matrix
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]

Mirror Matrix
[1, 4, 7]
[2, 5, 8]
[3, 6, 9]

Method 3: Using zip() Function

The zip() function provides the most concise way to transpose a matrix ?

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

print("Original Matrix")
for row in matrix:
    print(row)

# Mirror matrix using zip function
mirror_matrix = list(map(list, zip(*matrix)))

print("\nMirror Matrix")
for row in mirror_matrix:
    print(row)

Original Matrix
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]

Mirror Matrix
[1, 4, 7]
[2, 5, 8]
[3, 6, 9]

Comparison

Conclusion

All three methods effectively transpose a matrix by swapping rows and columns. Use the nested loop approach for clarity, list comprehension for Pythonic code, or zip() for the most concise solution.