CS146 Overview. Problem Solving by Computing Human Level Virtual Machine Actual Computer Virtual...

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

5 2 4 6 1 3

j=2

2

i=j-1=1 Key=2

A[1]>key 1>0

5 2

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