input: from typing import List
  
  def matching_paren(s: str) -> bool:
      """Check if the given string has matching parentheses.
      >>> matching_paren('(())')
      True
      >>> matching_paren('(()')
      False
      >>> matching_paren('())')
      False
      >>> matching_paren('')
      True
      >>> matching_paren('a(b)c')
      True
      """
      stack = []
      for char in s:
          if char == '(':
              stack.append(char)
          elif char == ')':
              if len(stack) == 0:
                  return False 
              stack.pop()
      
      return len(stack) == 0
output:     stack = []
      for char in s:
          if char == '(':
              stack.append(char)
          elif char == ')':
              if len(stack) == 0:
                  return False 
              stack.pop()
      
      return len(stack) == 0