Problem Description

YouYou will have 20–25 minutes per problem to implement the following two functions. Be prepared to explain your approach and analyze its time and space complexity for each.

Problem 1: Palindrome Check

Write a function that determines whether a given string is a palindrome.

• A string is a palindrome if it reads the same forward and backward.
• Compare characters exactly as they appear; do not perform case folding or ignore punctuation/whitespace unless you explicitly state and implement such behavior.

Function Signature Example:

bool is_palindrome(s: str)

Input:

• s: A string (which may be empty).

Output:

• true if s is a palindrome, otherwise false.

Examples:

• "abba" -> true
• "abc" -> false
• "" -> true

Problem 2: Valid Parentheses Sequence

Write a function that checks whether a string containing only parentheses characters is valid.

A string is valid if:

1. Every opening bracket has a corresponding closing bracket of the same type.
2. Brackets close in the correct order.

Assume the allowed bracket types are: (), [], {}.

Function Signature Example:

bool is_valid_parentheses(s: str)

Input:

• s: A string consisting only of characters from ()[]{} (which may be empty).

Output:

• true if s is valid, otherwise false.

Examples:

• "()" -> true
• "([]){}" -> true
• "(]" -> false
• "([)]" -> false
• "" -> true

Documentation Requirement

For each function, include a docstring with:

• Description
• Inputs/Outputs
• Callouts (assumptions, edge cases, complexity)