Interview Q&A / Data Structures & Algorithms

1. How do you find the longest substring without repeating characters?

   Use a sliding window. Expand the right end one character at a time and remember the last index where each character was seen. If the new character already appears inside the window, move the left end just past its previous position. Track the largest window size. This is O(n) time.

   AdvancedIn-depthCoding4 min read
2. How do you design an LRU cache with O(1) get and put?

   Combine a hash map for instant lookup with an ordering of recent use. In JavaScript a Map remembers insertion order, so deleting and re-inserting a key on each access moves it to the newest end; the oldest key is evicted when full.

   AdvancedQuick answerCoding1 min read