Is Spiral Matrix III easy or hard?

Spiral Matrix III is rated Medium because the logic for expanding spiral steps can be tricky at first. Once you recognize the pattern of increasing step lengths after every two directions, the implementation becomes straightforward.

Spiral Matrix III Python/Java solution

Both Python and Java implementations follow the same spiral simulation logic. Maintain direction vectors, track the current step length, and expand it after every two turns. Append coordinates to the result only when they fall within the grid bounds.

How to solve Spiral Matrix III in O(n)?

Treat n as the total number of cells (rows * cols). Simulate the spiral using a direction array and increase the step length after every two directions. During each step, check whether the current position lies inside the grid before adding it to the result list.

What is the best approach for Spiral Matrix III?

The best approach is spiral path simulation with expanding step lengths. Move in four directions (right, down, left, up) and increase the step size after every two turns. Record coordinates only when they fall inside the grid. This visits all cells in O(rows*cols) time using O(1) extra space.

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

Spiral traversal and matrix simulation problems frequently appear in interviews at companies like Amazon, Google, and Meta. Variants such as Spiral Matrix, Spiral Matrix II, and coordinate traversal questions test simulation logic and boundary handling.

What data structure is used in Spiral Matrix III?

The solution mainly uses arrays or lists to store the resulting coordinates and a small direction array to control movement. No advanced data structures are required; the core idea is controlled simulation over a matrix grid.

What is the time complexity of Spiral Matrix III?

The optimal solution runs in O(rows*cols) time because every valid cell in the grid is recorded exactly once. The spiral may step outside the grid temporarily, but the total useful operations remain proportional to the number of cells.

Description Solution Video 30:57

885. Spiral Matrix III

Medium84.6% acceptance8 companies

You start at the cell (rStart, cStart) of an rows x cols grid facing east. The northwest corner is at the first row and column in the grid, and the southeast corner is at the last row and column.

You will walk in a clockwise spiral shape to visit every position in this grid. Whenever you move outside the grid's boundary, we continue our walk outside the grid (but may return to the grid boundary later.). Eventually, we reach all rows * cols spaces of the grid.

Return an array of coordinates representing the positions of the grid in the order you visited them.

Example 1:

Input: rows = 1, cols = 4, rStart = 0, cStart = 0
Output: [[0,0],[0,1],[0,2],[0,3]]

Example 2:

Input: rows = 5, cols = 6, rStart = 1, cStart = 4
Output: [[1,4],[1,5],[2,5],[2,4],[2,3],[1,3],[0,3],[0,4],[0,5],[3,5],[3,4],[3,3],[3,2],[2,2],[1,2],[0,2],[4,5],[4,4],[4,3],[4,2],[4,1],[3,1],[2,1],[1,1],[0,1],[4,0],[3,0],[2,0],[1,0],[0,0]]

Constraints: