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.

Find the smallest substring within a larger string that contains all the characters of a target string. You need to locate the minimum window that satisfies this condition.

Transform one word into another, one letter at a time, using only words from a given dictionary. Find the shortest sequence of words to reach the target.