10 - Regular Expression Matching\.

Hard

Given an input string s and a pattern p, implement regular expression matching with support for '.' and '*' where:

• '.' Matches any single character.

• '*' Matches zero or more of the preceding element.

The matching should cover the entire input string (not partial).

Example 1:

Input: s = "aa", p = "a"

Output: false

Explanation: "a" does not match the entire string "aa".

Example 2:

Input: s = "aa", p = "a\*"

Output: true

Explanation: '\*' means zero or more of the preceding element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".

Example 3:

Input: s = "ab", p = ".\*"

Output: true

Explanation: ".\*" means "zero or more (\*) of any character (.)".

Example 4:

Input: s = "aab", p = "c\*a\*b"

Output: true

Explanation: c can be repeated 0 times, a can be repeated 1 time. Therefore, it matches "aab".

Example 5:

Input: s = "mississippi", p = "mis\*is\*p\*."

Output: false

Constraints:

• 1 <= s.length <= 20

• 1 <= p.length <= 30

• s contains only lowercase English letters.

• p contains only lowercase English letters, '.', and '*'.

• It is guaranteed for each appearance of the character '*', there will be a previous valid character to match.