// Regular Expression Matching — HARD
// Category: dynamic-programming
Given an input string `s` and a pattern `p`, implement regular expression matching with support for `'.'` and `'*'`.
- `'.'` matches any single character.
- `'*'` matches zero or more of the preceding element.
The matching must cover the **entire** input string.
Example: s = "aa", p = "a"
Output: false