LeetCode-in-All

10. Regular Expression Matching

Hard

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

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:

Solution

# @param {String} s
# @param {String} p
# @return {Boolean}
def is_match(s, p)
  converted = ''
  split = p.split('')
  split.each do |c|
    if c == '*'
      converted += '*'
    elsif c == '.'
      converted += '[a-z]'
    else
      converted += c
    end
  end
  s.match(converted).to_s == s
end