Spiral Matrix II · Interview Problem

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Spiral Matrix II

Generate an $n \times n$ matrix filled with numbers from 1 to $n^2$ in spiral order.

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Problem Statement

Problem

Given a positive integer $n$ , create an $n \times n$ matrix and fill it with the integers from 1 to n^2 in clockwise spiral order, starting from the top-left cell and moving right first.

You should return the completed matrix after all numbers have been placed.

Notes

The spiral proceeds around the outer layer first, then continues inward.
Each number from 1 to n^2 must appear exactly once.
When the spiral reaches the center, it should stop after placing the final value.

Input Format

A single integer n.

Interpretation

Build an n x n grid.
Fill cells with 1, 2, 3, ..., n^2 in clockwise spiral order.

Output Format

Return an n x n 2D integer array representing the filled spiral matrix.

Constraints

$1 \le n$ .
The matrix size is $n \times n$ .
Every value from 1 to n^2 appears exactly once.

Examples

Sample cases returned by the problem API.

Example 1

Input

n = 3

Output

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

Explanation

The numbers are placed in clockwise spiral order starting from the top-left corner.

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