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10. Regular Expression Matching
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Hard
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Given an input string s and a pattern p, implement regular expression matching with support for '.' and '*' where:
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'.' Matches any single character.
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'*' Matches zero or more of the preceding element.
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The matching should cover the entire input string (not partial).
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Example 1:
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Input: s = "aa", p = "a"
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Output: false
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Explanation: "a" does not match the entire string "aa".
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Example 2:
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Input: s = "aa", p = "a*"
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Output: true
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Explanation: '*' means zero or more of the preceding element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".
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Example 3:
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Input: s = "ab", p = ".*"
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Output: true
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Explanation: ".*" means "zero or more (*) of any character (.)".
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Constraints:
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1 <= s.length <= 20
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1 <= p.length <= 30
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s contains only lowercase English letters.
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p contains only lowercase English letters, '.', and '*'.
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It is guaranteed for each appearance of the character '*', there will be a previous valid character to match.
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