<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 {

public:

    const int dirs[4][2] = { {0, 1}, {1, 0}, {0, -1}, {-1, 0} };

    vector<vector<int>> generateMatrix(int n) {

        vector<vector<int>> ans(n, vector<int>(n));

        int i = 0, j = 0, k = 0;

        for (int v = 1; v <= n * n; ++v) {

            ans[i][j] = v;

            int x = i + dirs[k][0], y = j + dirs[k][1];

            if (x < 0 || y < 0 || x >= n || y >= n || ans[x][y]) {

                k = (k + 1) % 4;

                x = i + dirs[k][0], y = j + dirs[k][1];

            }

            i = x, j = y;

        }

        return ans;

    }

};

   
    
    

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