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
func generateMatrix(n int) [][]int {
	ans := make([][]int, n)
	for i := range ans {
		ans[i] = make([]int, n)
	}
	dirs := [5]int{0, 1, 0, -1, 0}
	i, j, k := 0, 0, 0
	for v := 1; v <= n*n; v++ {
		ans[i][j] = v
		x, y := i+dirs[k], j+dirs[k+1]
		if x < 0 || x >= n || y < 0 || y >= n || ans[x][y] != 0 {
			k = (k + 1) % 4
		}
		i += dirs[k]
		j += dirs[k+1]
	}
	return ans
}
