codejump
Academy

Data Structures

6 pages · about 81 min of reading

  1. 01Linked lists, singly and doublyWhy a linked list trades O(1) lookup for O(1) insertion, the sentinel, reversal and cycle-detection patterns interviewers ask for, and when it actually beats an array.
  2. 02Stacks and queues, LIFO and FIFOTwo disciplines built on the same array, why the call stack and the event queue are named what they are, and the monotonic-stack and two-stack patterns.
  3. 03Hash tables: hashing and collisionsHow a key becomes an array index, why collisions are the design, the counting and grouping patterns behind half of all interview questions, and what Map and dict do.
  4. 04Trees, tries, and traversal orderA hierarchy instead of a chain, the four traversal orders and when each applies, how a binary search tree stays fast, and the tree keyed by character.
  5. 05Heaps and priority queuesA tree that lives in a flat array, the one invariant that makes "give me the smallest" an O(log n) operation, and why sorting everything is the wrong tool for "top k".
  6. 06Graphs: BFS, DFS and topological sortNodes and edges instead of a fixed shape: BFS for shortest paths, DFS to flood a grid, topological sort for dependencies, and union-find for connectivity.