Regular Expression Matching

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).

Examples

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, so '.' repeated twice matches "ab".

Constraints

• 1 <= s.length <= 20
• 1 <= p.length <= 20
• s contains only lowercase English letters
• p contains only lowercase English letters, '.', and '*'
• It is guaranteed for each appearance of '*', there will be a previous valid character to match