CS146 Overview

Problem Solving by Computing Human Level  Virtual Machine   Actual Computer Virtual Machine Level L0

Languages, Levels, Virtual Machines A multilevel machine

Languages, Levels, Virtual Machines

Problem Solving by Computing Human Level (Algorithms)  Machine Level Ln (JAVA  )  

What is an Algorithm? An algorithm is a well-defined computational procedure that takes some value or set of values, as input and produce some value or set of values as output. A “tool” for solving a well-specified computational problem

Sorting Problem Input: A sequence of numbers (a1, a2,...) Output: A reording (a’1, a’2,...) of the input such that a’1  a’2 ...

Simple Sorting Algorithms 1.Insertion Sort 2.Merge Sort 3.Quick Sort

Simple Sorting Algorithms 1.Insertion Sort 2.Merge Sort 3.Quick Sort

Insertion Sort j  2 to length[A] Do A[j]  key  insert A[j] into A[1, 2, … j-1] i  j-1 While i > 0 and A[I]> key Do A[i+1]  A[i] i  i-1 A[i+1]  key

j=2 2 i=j-1=1Key=2 A[1]>k ey 1>0 52

Latent Semantic Index Project: Compute the LSI (Latent Semantic Index) of a set of web pages/text files, such as Google’s return. Sort a web page or a text file (XML or Text) in alphabetical order

Latent Semantic Index 1.Sort a web page or a text file (XML or Text) 2. Create an Inverted file Attached to each words a list of locations that this word has appeared

Latent Semantic Index 1.Applications 2.Use LSI, we can cluster (classify) the return of Google’s search into meaningful group