Is Spiral Matrix II easy or hard?

Spiral Matrix II is generally classified as Medium difficulty. The algorithm itself is straightforward, but careful boundary updates and edge-case handling are required to avoid overwriting cells or missing the final layer.

Spiral Matrix II Python/Java solution

Python and Java implementations follow the same boundary logic: create an n x n matrix, track top/bottom/left/right boundaries, and fill numbers sequentially while shrinking the boundaries. Both versions run in O(n^2) time with constant extra space.

How to solve Spiral Matrix II in O(n^2)?

Use spiral boundary simulation. Initialize four pointers (top, bottom, left, right) and fill the matrix in four directions: left→right, top→bottom, right→left, and bottom→top. After each pass, move the corresponding boundary inward until all n^2 cells are filled.

What is the best approach for Spiral Matrix II?

The boundary-based spiral simulation is the most common solution. Track four boundaries (top, bottom, left, right) and fill the matrix layer by layer while shrinking these boundaries after each pass. The algorithm writes each number exactly once, resulting in O(n^2) time and O(1) extra space.

Is Spiral Matrix II asked at Google/Amazon/Meta?

Spiral traversal problems frequently appear in interviews at companies like Amazon, Google, and Meta because they test matrix indexing, boundary control, and careful simulation logic. Variants such as Spiral Matrix traversal and spiral generation are common interview questions.

What data structure is used in Spiral Matrix II?

The primary data structure is a 2D array (matrix). The algorithm fills this matrix using index manipulation and directional traversal. No additional complex structures are required beyond a few integer variables for boundaries or directions.

What is the time complexity of Spiral Matrix II?

The time complexity is O(n^2) because the algorithm fills every cell in the n x n matrix exactly once. Each assignment writes the next number in the spiral sequence until all n^2 positions are filled. Extra space complexity is O(1) excluding the output matrix.

Description Solution Video 6:25

59. Spiral Matrix II

Medium76.0% acceptance11 companies

Given a positive integer n, generate an n x n matrix filled with elements from 1 to n² in spiral order.

Example 1:

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

Example 2:

Input: n = 1
Output: [[1]]

Constraints:

1 <= n <= 20

Asked at 11 companies

eBay Amazon Microsoft Zoho Adobe

Google Meta Bloomberg Tiktok Goldman Sachs

TCS

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6:25

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59. Spiral Matrix II

Asked at 11 companies

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