Domino and Tromino Tiling
<p>You have two types of tiles: a <code>2 x 1</code> domino shape and a tromino shape. You may rotate these shapes.</p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0700-0799/0790.Domino%20and%20Tromino%20Tiling/images/lc-domino.jpg" style="width: 362px; height: 195px;" />
<p>Given an integer n, return <em>the number of ways to tile an</em> <code>2 x n</code> <em>board</em>. Since the answer may be very large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>In a tiling, every square must be covered by a tile. Two tilings are different if and only if there are two 4-directionally adjacent cells on the board such that exactly one of the tilings has both squares occupied by a tile.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0700-0799/0790.Domino%20and%20Tromino%20Tiling/images/lc-domino1.jpg" style="width: 500px; height: 226px;" />
<pre>
<strong>Input:</strong> n = 3
<strong>Output:</strong> 5
<strong>Explanation:</strong> The five different ways are shown above.
</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;= 1000</code></li>
</ul>
Dynamic Programming
class Solution {
    public int numTilings(int n) {
        long[] f = {1, 0, 0, 0};
        int mod = (int) 1e9 + 7;
        for (int i = 1; i <= n; ++i) {
            long[] g = new long[4];
            g[0] = (f[0] + f[1] + f[2] + f[3]) % mod;
            g[1] = (f[2] + f[3]) % mod;
            g[2] = (f[1] + f[3]) % mod;
            g[3] = f[0];
            f = g;
        }
        return (int) f[0];
    }
}