Spiral Matrix

Spiral Matrix is a classic interview problem tagged with Array, Matrix, and Simulation, commonly asked by Microsoft. It requires traversing a 2D matrix in a clockwise spiral starting from the top-left corner.[1][10]

Problem Statement

Given an m x n matrix, return all elements of the matrix in spiral order. The spiral starts at the top-left corner and moves right, then down, then left, then up, continuing inward layer by layer until all elements are covered.[10][1]

Example Inputs/Outputs

For a standard 4x4 matrix: Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]] Output: [1,2,3,4,8,12,16,15,14,13,9,5,6,10,11,7] This traces: right → down → left → up → right → down → left → up.[7][1]

Single row example: Input: matrix = [[1,2,3,4]] Output: [1,2,3,4] Single column example: Input: matrix = [[1],[2],[3],[4]] Output: [1,2,3,4] Empty matrix: Input: matrix = [] Output: [] Irregular shape (2x3): Input: matrix = [[1,2,3],[4,5,6]] Output: [1,2,3,6,5,4]

Constraints

• m == matrix.length (rows)
• n == matrix[i].length (columns)
• 1 ≤ m, n ≤ 10
• -100 ≤ matrix[i][j] ≤ 100 These ensure the matrix is small, non-empty in dimensions, and fits typical interview bounds.[3][10]