279\. Perfect Squares

Medium

Given an integer `n`, return _the least number of perfect square numbers that sum to_ `n`.

A **perfect square** is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, `1`, `4`, `9`, and `16` are perfect squares while `3` and `11` are not.

**Example 1:**

**Input:** n = 12

**Output:** 3

**Explanation:** 12 = 4 + 4 + 4. 

**Example 2:**

**Input:** n = 13

**Output:** 2

**Explanation:** 13 = 4 + 9. 

**Constraints:**

*   <code>1 <= n <= 10<sup>4</sup></code>