<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://assets.leetcode.com/uploads/2020/11/13/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>

class Solution:
    def generateMatrix(self, n: int) -> List[List[int]]:
        res = [[0] * n for _ in range(n)]
        left, right = 0, n - 1
        top, bottom = 0, n - 1
        val = 1

        while left <= right and top <= bottom:
            # fill in top row
            for c in range(left, right + 1):
                res[top][c] = val
                val += 1
            top += 1

            # fill in right col
            for r in range(top, bottom + 1):
                res[r][right] = val
                val += 1
            right -= 1

            # if not (left <= right and top <= bottom):
            #     break

            # fill in bottom row
            for c in range(right, left - 1, -1):
                res[bottom][c] = val
                val += 1
            bottom -= 1

            # fill in left col
            for r in range(bottom, top - 1, -1):
                res[r][left] = val
                val += 1
            left += 1

        return res


        
16600