Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...
) which sum to n.
Example 1:
Input: n =12
Output: 3 Explanation:12 = 4 + 4 + 4.
Example 2:
Input: n =13
Output: 2 Explanation:13 = 4 + 9.