def longest_common_substring(str1: str, str2: str) -> str:
    """
    Find the longest common substring of two strings using a suffix tree.
 
    Args:
        str1: First string
        str2: Second string
 
    Returns:
        The longest common substring
    """
    # Concatenate the strings with a unique separator
    combined = str1 + "#" + str2 + "$"
 
    # Build a suffix tree for the combined string
    # Traverse the tree to find the longest path that occurs in both strings
 
    return longest_substring
 
def longest_common_substring_multiple(strings: list[str]) -> str:
    """
    Find the longest common substring among multiple strings using suffix structures.
 
    Args:
        strings: List of strings to compare
 
    Returns:
        The longest common substring that appears in all strings
    """
    # Implement an algorithm to find the longest common substring in multiple strings
    # You may use either suffix trees or suffix arrays
 
    pass
 
def longest_palindromic_substring(text: str) -> str:
    """
    Find the longest palindromic substring in a given text using suffix structures.
 
    Args:
        text: Input text
 
    Returns:
        The longest palindromic substring
    """
    # Create a new string concatenating the original text and its reverse
    # Use suffix structures to find the longest common substring between them
    # Handle the case where palindrome centers between characters
 
    pass