Tripadvisor

Find the common characters that appear in all strings within a given array of strings. Return these common characters as a list.

Determine if a string containing parentheses is valid. A valid string has matching and properly nested opening and closing parentheses.

Design a data structure that acts as a Least Recently Used (LRU) cache. Implement methods to get and put key-value pairs, evicting the least recently used entry when the cache is full.