Spiral Matrix II
<p>Given a positive integer <code>n</code>, generate an <code>n x n</code> <code>matrix</code> filled with elements from <code>1</code> to <code>n<sup>2</sup></code> in spiral order.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0000-0099/0059.Spiral%20Matrix%20II/images/spiraln.jpg" style="width: 242px; height: 242px;" />
<pre>
<strong>Input:</strong> n = 3
<strong>Output:</strong> [[1,2,3],[8,9,4],[7,6,5]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> [[1]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 20</code></li>
</ul>
Array; Matrix; Simulation
class Solution:
    def generateMatrix(self, n: int) -> List[List[int]]:
        ans = [[0] * n for _ in range(n)]
        dirs = (0, 1, 0, -1, 0)
        i = j = k = 0
        for v in range(1, n * n + 1):
            ans[i][j] = v
            x, y = i + dirs[k], j + dirs[k + 1]
            if x < 0 or x >= n or y < 0 or y >= n or ans[x][y]:
                k = (k + 1) % 4
            i, j = i + dirs[k], j + dirs[k + 1]
        return ans
