Python program to print matrix in a snake pattern

In this article, we will learn how to print a matrix in a snake pattern. A snake pattern prints the first row left to right, the second row right to left, the third row left to right, and so on, creating a zigzag or snake-like traversal.

We will explore two different approaches to accomplish this task using Python.

What is a Snake Pattern?

Given a matrix, the snake pattern traversal means:

• Print even-indexed rows (0, 2, 4...) from left to right

• Print odd-indexed rows (1, 3, 5...) from right to left

For example, a 3×3 matrix would be traversed as: 1?2?3, 6?5?4, 7?8?9.

Method 1: Using Nested For Loop

This approach checks if the row index is even or odd and prints accordingly ?

def printSnakePattern(matrix):
    rows = len(matrix)
    columns = len(matrix[0])
    
    for i in range(rows):
        if i % 2 == 0:  # Even row - left to right
            for j in range(columns):
                print(matrix[i][j], end=" ")
        else:  # Odd row - right to left
            for j in range(columns - 1, -1, -1):
                print(matrix[i][j], end=" ")

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

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

print("\nSnake Pattern:")
printSnakePattern(matrix)

Given Matrix:
[1, 2, 3, 4]
[5, 6, 7, 8]
[9, 10, 11, 12]
[13, 14, 15, 16]

Snake Pattern:
1 2 3 4 8 7 6 5 9 10 11 12 16 15 14 13 

Method 2: Using Slicing to Reverse Alternate Rows

This method reverses odd-indexed rows using Python's slice notation [::-1] before printing ?

def printSnakePatternSlicing(matrix):
    rows = len(matrix)
    columns = len(matrix[0])
    
    # Create a copy to avoid modifying original matrix
    temp_matrix = [row[:] for row in matrix]
    
    # Reverse alternate rows (odd-indexed rows)
    for i in range(rows):
        if i % 2 != 0:
            temp_matrix[i] = temp_matrix[i][::-1]
    
    # Print the modified matrix
    for i in range(rows):
        for j in range(columns):
            print(temp_matrix[i][j], end=" ")

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

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

print("\nSnake Pattern:")
printSnakePatternSlicing(matrix)

Given Matrix:
[1, 2, 3, 4]
[5, 6, 7, 8]
[9, 10, 11, 12]
[13, 14, 15, 16]

Snake Pattern:
1 2 3 4 8 7 6 5 9 10 11 12 16 15 14 13 

Comparison

Conclusion

Both methods effectively print a matrix in snake pattern. The nested loop approach is more memory-efficient, while the slicing method offers cleaner code. Choose based on your requirements for memory usage and code readability.