<p>Given an integer <code>n</code>, return <em>the least number of perfect square numbers that sum to</em> <code>n</code>.</p> <p>A <strong>perfect square</strong> is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, <code>1</code>, <code>4</code>, <code>9</code>, and <code>16</code> are perfect squares while <code>3</code> and <code>11</code> are not.</p> <p> </p> <p><strong class="example">Example 1:</strong></p> <pre> <strong>Input:</strong> n = 12 <strong>Output:</strong> 3 <strong>Explanation:</strong> 12 = 4 + 4 + 4. </pre> <p><strong class="example">Example 2:</strong></p> <pre> <strong>Input:</strong> n = 13 <strong>Output:</strong> 2 <strong>Explanation:</strong> 13 = 4 + 9. </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= n <= 10<sup>4</sup></code></li> </ul>