CSE 326 Course Review David Kaplan Dept of Computer Science & Engineering Autumn 2001

Course ReviewCSE 326 Autumn Why (did we) study data structures? Clever ways to organize information in order to enable efficient computation Systems Theory AI Graphics Applications DataStructures Databases NetworkingGames

Course ReviewCSE 326 Autumn Why (did we) take CSE 326?  Guaranteed non-obsolescence  May be most important CS course you ever take  Gain concepts, plans and mechanisms for creating better software

Course ReviewCSE 326 Autumn Course Goals  Learn some of the fundamental data structures in computer science  Learn to solve problems abstractly  Data structures are the building blocks  Learn to analyze and improve algorithms  Prove correctness  Gauge and improve time complexity  Learn UNIX  Required in upcoming courses

Course ReviewCSE 326 Autumn Concepts, Plans, Mechanisms Concepts  A list that lets me store and retrieve things  A tree that lets me store and retrieve things by hierarchy  A table that lets me store and retrieve things by name  A graph (network) that represents distances between cities, relationships between people, tasks within a project, etc.  and so on …

Course ReviewCSE 326 Autumn Concepts, Plans, Mechanisms Plans  Pseudocode  Block Diagrams  Flowcharts Mechanisms  Working code Intuition is the bridge concepts  plans  mechanisms

Course ReviewCSE 326 Autumn Organizing Information Concepts Simple collectionCollection with hierarchy Collection with complex topology Plans (ADTs) List, Stack, Queue Binary Search Tree, B-Tree, AVL Tree, Heaps, … Directed Graph, DAG, Flow Network, … MechanismsNumerous “Linear”“Hierarchical”“Graphical”

Course ReviewCSE 326 Autumn Using Organized Information Examples  Dictionary ADT  Store, retrieve, update, delete to-from large bodies of information  Priority queue ADT  Handle “priority” on-the-fly  Disjoint Sets ADT  Handle dynamic equivalence on-the-fly  Graph {ADT, data structure, ???}  Answer hard questions (sometimes efficiently!)  Shortest paths, spanning trees, …

Course ReviewCSE 326 Autumn Asymptotic Complexity How the running time of an algorithm scales with the size of its input Ways to measure complexity  Worst case  Average case  Amortized over a series of (presumably representative) runs  Best case (occasionally useful)

Course ReviewCSE 326 Autumn Apocalyptic Laptop Seth Lloyd, a physicist at the Massachusetts Institute of Technology, has calculated how to make PCs almost unimaginably faster--if you don't mind working on a black hole. Lloyd has used the laws of thermodynamics, information, relativity, and quantum mechanics to figure out the ultimate physical limits on the speed of a computer… Lloyd's ultimate laptop would convert all of its 1-kilogram mass into energy via Einstein's famous equation E = mc 2, thus turning itself into a billion-degree blob of plasma. "This would present a packaging problem," Lloyd admits … The computer would be capable of performing operations per second. - Charles Seife, Science Magazine, Vol 289, No 5484, Sep , pp

Course ReviewCSE 326 Autumn Big Bang ApocaLap, 1 year ApocaLap, 1 sec 1000 MIPS since Big Bang 1000 MIPS, 1 day

Course ReviewCSE 326 Autumn Stuff we did  Lists  Stacks  Queues  Search trees, in many flavors (BST, AVL, splay)  Heaps, in many flavors (binary, d, leftist, skew)  Hashing  Graphs, spanning trees  Graph algorithms (Dijkstra’s, Kruskal’s, Prim’s)  Asymptotic complexity  Recursion analysis  Sorting, in many flavors  Randomization (treaps, skip lists)

Course ReviewCSE 326 Autumn Stuff we didn’t get to  Algorithm Design  Greedy  Divide and conquer  Backtracking  Dynamic programming  Amortized Analysis (formal mechanisms)  NP-Completeness  At least enough to qualitatively distinguish P and NP problems : - (

Course ReviewCSE 326 Autumn Are we convinced yet? Mastery of this material separates you from …

Course ReviewCSE 326 Autumn Coming Attractions  Wed Dec 12: wrap-up and closing ceremony  Wed Dec 12 3:30-4:30pm: Case Study  Better Living through Graphs and Trees  Sun Dec 16: Final Exam Review Session  Time/place TBD To do study for … Final Exam Mon, Dec 17 2:30pm, MGH 389