Is Spiral Matrix easy or hard?

Spiral Matrix is considered a medium difficulty problem. The core idea is straightforward, but correctly updating boundaries and avoiding duplicate traversal when rows or columns collapse requires careful implementation.

How to solve Spiral Matrix in O(n)?

For an m×n matrix, the optimal complexity is O(m×n) because every element must be visited to produce the output order. The typical solution uses boundary pointers to simulate spiral movement across rows and columns. This ensures each element is appended once while maintaining constant extra space.

What is the best approach for Spiral Matrix?

The best approach uses iterative boundary management. Maintain four pointers (top, bottom, left, right) and traverse the matrix edges while shrinking the boundaries after each direction. Every element is visited exactly once, giving O(m×n) time and O(1) extra space. This is the solution most interviewers expect.

What data structure is used in Spiral Matrix?

The problem primarily uses a 2D array (matrix). The algorithm relies on index boundaries rather than additional data structures, which keeps space complexity at O(1). The result is stored in a list or array while traversing the matrix in spiral order.

What is the time complexity of Spiral Matrix?

The time complexity is O(m×n) where m is the number of rows and n is the number of columns. Each matrix element is processed exactly once during the spiral traversal. No repeated scans occur, so the runtime grows linearly with the number of elements.

Spiral Matrix Python or Java solution approach?

Both Python and Java implementations follow the same logic: maintain four boundaries and iterate across rows or columns depending on the current direction. After each traversal, update the boundary pointer. The algorithm remains O(m×n) time and O(1) extra space regardless of language.

Is Spiral Matrix asked at Google, Amazon, or Meta?

Spiral Matrix appears frequently in coding interviews at large tech companies including Amazon, Google, and Meta. The problem tests matrix traversal, careful index management, and edge‑case handling when rows or columns shrink during iteration.

Description Hints 3 Solution Video 16:33

54. Spiral Matrix

Medium58.2% acceptance49 companies

Given an m x n matrix, return all elements of the matrix in spiral order.

Example 1:

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

Example 2:

Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

Constraints:

m == matrix.length
n == matrix[i].length
1 <= m, n <= 10
-100 <= matrix[i][j] <= 100

Asked at top 20 of 49 companies

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Topics

Hints open one at a time

Hint 1

Well for some problems, the best way really is to come up with some algorithms for simulation. Basically, you need to simulate what the problem asks us to do.

Hint 2

We go boundary by boundary and move inwards. That is the essential operation. First row, last column, last row, first column, and then we move inwards by 1 and repeat. That's all. That is all the simulation that we need.

Hint 3

Think about when you want to switch the progress on one of the indexes. If you progress on i out of [i, j], you'll shift in the same column. Similarly, by changing values for j, you'd be shifting in the same row. Also, keep track of the end of a boundary so that you can move inwards and then keep repeating. It's always best to simulate edge cases like a single column or a single row to see if anything breaks or not.

16:33

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