Spiral Matrix Traversal in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Spiral Traversal on 3x3 Matrix

What is the output of the spiral traversal on the following 3x3 matrix?

Matrix:
1 2 3
4 5 6
7 8 9

DSA Python

def spiral_traversal(matrix):
    result = []
    top, bottom = 0, len(matrix) - 1
    left, right = 0, len(matrix[0]) - 1
    while left <= right and top <= bottom:
        for i in range(left, right + 1):
            result.append(matrix[top][i])
        top += 1
        for i in range(top, bottom + 1):
            result.append(matrix[i][right])
        right -= 1
        if top <= bottom:
            for i in range(right, left - 1, -1):
                result.append(matrix[bottom][i])
            bottom -= 1
        if left <= right:
            for i in range(bottom, top - 1, -1):
                result.append(matrix[i][left])
            left += 1
    return result

print(spiral_traversal([[1,2,3],[4,5,6],[7,8,9]]))

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

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

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

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

💡 Hint

Follow the edges of the matrix clockwise, moving inward layer by layer.

The spiral traversal starts at the top-left corner and moves right, then down, then left, then up, shrinking the boundaries after each direction until all elements are visited.

❓ Predict Output

intermediate

Spiral Traversal Output for Rectangular Matrix

What is the spiral traversal output of this 3x4 matrix?

Matrix:
1 2 3 4
5 6 7 8
9 10 11 12

DSA Python

def spiral_traversal(matrix):
    result = []
    top, bottom = 0, len(matrix) - 1
    left, right = 0, len(matrix[0]) - 1
    while left <= right and top <= bottom:
        for i in range(left, right + 1):
            result.append(matrix[top][i])
        top += 1
        for i in range(top, bottom + 1):
            result.append(matrix[i][right])
        right -= 1
        if top <= bottom:
            for i in range(right, left - 1, -1):
                result.append(matrix[bottom][i])
            bottom -= 1
        if left <= right:
            for i in range(bottom, top - 1, -1):
                result.append(matrix[i][left])
            left += 1
    return result

print(spiral_traversal([[1,2,3,4],[5,6,7,8],[9,10,11,12]]))

A [1, 5, 9, 10, 11, 12, 8, 4, 3, 2, 6, 7]

B [1, 4, 8, 12, 11, 10, 9, 5, 6, 7, 3, 2]

C [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

D [1, 2, 3, 4, 8, 12, 11, 10, 9, 5, 6, 7]

💡 Hint

Traverse the outer layer first, then move inward.

The traversal goes right across the top row, down the last column, left across the bottom row, and up the first column, then repeats for the inner layers.

🔧 Debug

advanced

Identify the Error in Spiral Traversal Code

The following code is intended to perform spiral traversal on a matrix. What error will it raise when run on a 1x1 matrix?

Matrix:
[[1]]

DSA Python

def spiral_traversal(matrix):
    result = []
    top, bottom = 0, len(matrix) - 1
    left, right = 0, len(matrix[0]) - 1
    while left < right and top < bottom:
        for i in range(left, right + 1):
            result.append(matrix[top][i])
        top += 1
        for i in range(top, bottom + 1):
            result.append(matrix[i][right])
        right -= 1
        for i in range(right, left - 1, -1):
            result.append(matrix[bottom][i])
        bottom -= 1
        for i in range(bottom, top - 1, -1):
            result.append(matrix[i][left])
        left += 1
    return result

print(spiral_traversal([[1]]))

A [1, 2, 4, 3]

B [] (empty list)

C IndexError

D Infinite loop

💡 Hint

Check the loop condition for small matrices.

The loop condition uses < instead of <=, so for 1x1 matrix the while loop never runs and returns empty list.

🚀 Application

advanced

Number of Elements Visited in Spiral Traversal

Given a 4x5 matrix, how many elements will be visited during a complete spiral traversal?

A 9

B 18

C 20

D 10

💡 Hint

Count all elements in the matrix.

Spiral traversal visits every element exactly once, so total elements visited equals rows * columns = 4 * 5 = 20.

🧠 Conceptual

expert

Why Use Four Pointers in Spiral Traversal?

In spiral traversal of a matrix, why do we maintain four pointers (top, bottom, left, right)?

A To keep track of the current boundaries of the unvisited matrix area

B To store the values of the first row, last row, first column, and last column

C To count the total number of elements visited in each direction

D To mark the visited elements in the matrix

💡 Hint

Think about how the traversal shrinks the area it covers after each pass.

The four pointers define the current edges of the matrix section that still needs to be traversed in spiral order. They move inward after each side is processed.