Spiral Matrix Traversal in DSA Python - Build from Scratch

Spiral Matrix Traversal

📖 Scenario: You are working with a 2D grid of numbers, like a map or a spreadsheet. You want to collect all the numbers by moving around the edges first, then moving inward in a spiral pattern.

🎯 Goal: Build a program that takes a fixed 3x3 matrix and prints the numbers in the order you would see if you walked around the matrix in a spiral, starting from the top-left corner and moving right.

📋 What You'll Learn

Create a 3x3 matrix called matrix with the exact values [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

Create variables top, bottom, left, and right to track the current edges of the matrix

Use a while loop to traverse the matrix in a spiral order using the edge variables

Collect the spiral order elements in a list called result

Print the result list at the end

💡 Why This Matters

🌍 Real World

Spiral traversal is useful in image processing, game development, and reading data in a pattern that covers all edges first.

💼 Career

Understanding matrix traversal helps in technical interviews and solving problems related to grids, maps, and 2D data structures.

1

Create the 3x3 matrix

Create a variable called matrix and set it to the exact 3x3 list of lists: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

DSA Python

# Create the 3x3 matrix called matrix
# Your code here

Hint

Use square brackets to create a list of lists exactly as shown.

2

Set up edge variables

Create variables top, bottom, left, and right and set them to 0, 2, 0, and 2 respectively to represent the edges of the matrix

DSA Python

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
# Set edge variables top, bottom, left, right
# Your code here

Hint

These variables mark the current edges of the matrix as you move inward.

3

Traverse the matrix in spiral order

Create an empty list called result. Use a while loop with the condition left <= right and top <= bottom. Inside the loop, add elements from the top row, right column, bottom row, and left column to result in spiral order. Update top, bottom, left, and right after each side is processed.

DSA Python

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
top = 0
bottom = 2
left = 0
right = 2
# Create result list and write the spiral traversal loop
# Your code here

Hint

Remember to move the edges inward after processing each side.

4

Print the spiral order result

Write a print statement to display the result list.

DSA Python

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
top = 0
bottom = 2
left = 0
right = 2
result = []
while left <= right and top <= bottom:
    for col in range(left, right + 1):
        result.append(matrix[top][col])
    top += 1
    for row in range(top, bottom + 1):
        result.append(matrix[row][right])
    right -= 1
    if top <= bottom:
        for col in range(right, left - 1, -1):
            result.append(matrix[bottom][col])
        bottom -= 1
    if left <= right:
        for row in range(bottom, top - 1, -1):
            result.append(matrix[row][left])
        left += 1
# Print the result list
# Your code here

Hint

The printed list should show the numbers in spiral order.