delphi - the tomes of delphi - algorithms and data structures

TEAMFLY Team-Fly ® The Tomes of Delphi ™ Algorithms and Data Structures Julian Bucknall Wordware Publishing, Inc. Library of Congress Cataloging-in-Publication Data Bucknall, Julian Tomes of Delphi: algorithms and data structures / by Julian Bucknall. p. cm. Includes bibliographical references and index. ISBN 1-55622-736-1 (pbk. : alk. paper) 1. Computer software—Development. 2. Delphi (Computer file). 3. Computer algorithms. 4. Data structures (Computer science) I. Title. QA76.76.D47 .B825 2001 2001033258 005.1 dc21 CIP © 2001, Wordware Publishing, Inc. Code © 2001, Julian Bucknall All Rights Reserved 2320 Los Rios Boulevard Plano, Texas 75074 No part of this book may be reproduced in any form or by any means without permission in writing from Wordware Publishing, Inc. Printed in the United States of America ISBN 1-55622-736-1 10987654321 0105 Delphi is a trademark of Inprise Corporation. Other product names mentioned are used for identification purposes only and may be trademarks of their respective companies. All inquiries for volume purchases of this book should be addressed to Wordware Publishing, Inc., at the above address. Telephone inquiries may be made by calling: (972) 423-0090 For Donna and the Greek cats iii Contents Introduction x Chapter 1 What is an Algorithm? 1 What is an Algorithm? 1 Analysis of Algorithms 3 The Big-Oh Notation 6 Best, Average, and Worst Cases 8 Algorithms and the Platform 8 Virtual Memory and Paging 9 Thrashing 10 Locality of Reference 11 The CPU Cache 12 Data Alignment 12 Space Versus Time Tradeoffs 14 Long Strings 16 Use const 17 Be Wary of Automatic Conversions 17 Debugging and Testing 18 Assertions 19 Comments 22 Logging 22 Tracing 22 Coverage Analysis 23 Unit Testing 23 Debugging 25 Summary 26 Chapter 2 Arrays 27 Arrays 27 Array Types in Delphi 28 Standard Arrays 28 Dynamic Arrays 32 New-style Dynamic Arrays 40 TList Class, an Array of Pointers 41 Overview of the TList Class 41 TtdObjectList Class 43 v Arrays on Disk 49 Summary 62 Chapter 3 Linked Lists, Stacks, and Queues 63 Singly Linked Lists 63 Linked List Nodes 65 Creating a Singly Linked List 65 Inserting into and Deleting from a Singly Linked List 65 Traversing a Linked List 68 Efficiency Considerations 69 Using a Head Node 69 Using a Node Manager 70 The Singly Linked List Class 76 Doubly Linked Lists 84 Inserting and Deleting from a Doubly Linked List 85 Efficiency Considerations 88 Using Head and Tail Nodes 88 Using a Node Manager 88 The Doubly Linked List Class 88 Benefits and Drawbacks of Linked Lists 96 Stacks 97 Stacks Using Linked Lists 97 Stacks Using Arrays 100 Example of Using a Stack 103 Queues 105 Queues Using Linked Lists 106 Queues Using Arrays 109 Summary 113 Chapter 4 Searching 115 Compare Routines 115 Sequential Search 118 Arrays 118 Linked Lists 122 Binary Search 124 Arrays 124 Linked Lists 126 Inserting into Sorted Containers 129 Summary 131 Chapter 5 Sorting 133 Sorting Algorithms 133 Shuffling a TList 136 Sort Basics 138 Slowest Sorts 138 Bubble Sort 138 vi Contents Shaker Sort 140 Selection Sort 142 Insertion Sort 144 Fast Sorts 147 Shell Sort 147 Comb Sort 150 Fastest Sorts 152 Merge Sort 152 Quicksort 161 Merge Sort with Linked Lists 176 Summary 181 Chapter 6 Randomized Algorithms 183 Random Number Generation 184 Chi-Squared Tests 185 Middle-Square Method 188 Linear Congruential Method 189 Testing 194 The Uniformity Test 195 TheGapTest 195 The Poker Test 197 The Coupon Collector’s Test 198 Results of Applying Tests 200 Combining Generators 201 Additive Generators 203 Shuffling Generators 205 Summary of Generator Algorithms 207 Other Random Number Distributions 208 Skip Lists 210 Searching through a Skip List 211 Insertion into a Skip List 215 Deletion from a Skip List 218 Full Skip List Class Implementation 219 Summary 225 Chapter 7 Hashing and Hash Tables 227 Hash Functions 228 Simple Hash Function for Strings 230 The PJW Hash Functions 230 Collision Resolution with Linear Probing 232 Advantages and Disadvantages of Linear Probing 233 Deleting Items from a Linear Probe Hash Table 235 The Linear Probe Hash Table Class 237 Other Open-Addressing Schemes 245 Quadratic Probing 246 vii Contents Pseudorandom Probing 246 Double Hashing 247 Collision Resolution through Chaining 247 Advantages and Disadvantages of Chaining 248 The Chained Hash Table Class 249 Collision Resolution through Bucketing 259 Hash Tables on Disk 260 Extendible Hashing 261 Summary 276 Chapter 8 Binary Trees 277 Creating a Binary Tree 279 Insertion and Deletion with a Binary Tree 279 Navigating through a Binary Tree 281 Pre-order, In-order, and Post-order Traversals 282 Level-order Traversals 288 Class Implementation of a Binary Tree 289 Binary Search Trees 295 Insertion with a Binary Search Tree 298 Deletion from a Binary Search Tree 300 Class Implementation of a Binary Search Tree 303 Binary Search Tree Rearrangements 304 Splay Trees 308 Class Implementation of a Splay Tree 309 Red-Black Trees 312 Insertion into a Red-Black Tree 314 Deletion from a Red-Black Tree 319 Summary 329 Chapter 9 Priority Queues and Heapsort 331 The Priority Queue 331 First Simple Implementation 332 Second Simple Implementation 335 The Heap 337 Insertion into a Heap 338 Deletion from a Heap 338 Implementation of a Priority Queue with a Heap 340 Heapsort 345 Floyd’s Algorithm 345 Completing Heapsort 346 Extending the Priority Queue 348 Re-establishing the Heap Property 349 Finding an Arbitrary Item in the Heap 350 Implementation of the Extended Priority Queue 350 Summary 356 viii Contents Chapter 10 State Machines and Regular Expressions 357 State Machines 357 Using State Machines: Parsing 357 Parsing Comma-Delimited Files 363 Deterministic and Non-deterministic State Machines 366 Regular Expressions 378 Using Regular Expressions 380 Parsing Regular Expressions 380 Compiling Regular Expressions 387 Matching Strings to Regular Expressions 399 Summary 407 Chapter 11 Data Compression 409 Representations of Data 409 Data Compression 410 Types of Compression 410 Bit Streams 411 Minimum Redundancy Compression 415 Shannon-Fano Encoding 416 Huffman Encoding 421 Splay Tree Encoding 435 Dictionary Compression 445 LZ77 Compression Description 445 Encoding Literals Versus Distance/Length Pairs 448 LZ77 Decompression 449 LZ77 Compression 456 Summary 467 Chapter 12 Advanced Topics 469 Readers-Writers Algorithm 469 Producers-Consumers Algorithm 478 Single Producer, Single Consumer Model 478 Single Producer, Multiple Consumer Model 486 Finding Differences between Two Files 496 Calculating the LCS of Two Strings 497 Calculating the LCS of Two Text Files 511 Summary 514 Epilogue 515 References 516 Index 518 Contents ix [...]... longint and pointer variables are also aligned on a 4-byte or 32-bit boundary If they are not and they straddle a 4-byte boundary, the CPU has to issue two reads to the cache, the first read to get the first part of the variable and the second read to get the second part The CPU then stitches together the value from these two parts, throwing away the bytes it doesn’t need (On other processors, the CPU... out of the user and producing some kind of output for her The standard algorithms have been developed and refined by computer scientists for use in the programming trenches by the likes of you and me Mastering the basic algorithms gives you a handle on your craft and on the language you use For example, if you know about hash tables, their strengths and weaknesses, what they are used for and why, and. .. consideration is given to real-life, drop-in -and- use application of the technique being discussed Even worse, from the viewpoint of the commercial programmer, many are textbooks to be used in a college or university course and hence some of the more interesting topics are left as exercises for the reader, with little or no answers Of course, the vast majority of them don’t use Delphi, Kylix, or Pascal Some... polymorphism, and delegation The object model in Delphi shouldn’t scare you! Having said that, a lot of the concepts described in this book are simple in the extreme A beginner programmer should find much in the book to teach him xii Introduction or her the basics of standard algorithms and data structures Indeed, looking at the code should teach such a programmer many tips and tricks of the advanced... 12, and little pieces here and there, the code will compile and run with any version of Delphi Apart from the small amount of the versionspecific code I have just mentioned, I have tested all code in this book with all versions of Delphi and with Kylix You can therefore assume that all code printed in this book will work with every version of Delphi Some code listings are version-specific though, and. .. What Will I Find, and Where? This book is divided into 12 chapters and a reference section Chapter 1 lays out some ground rules It starts off by discussing performance We’ll look at measurement of the efficiency of algorithms, starting out with the big-Oh notation, continuing with timing of the actual run time of algorithms, and finishing with the use of profilers We shall discuss data representation... is perfectly possible to code standard algorithms in Delphi without using these Delphispecific language constructs, it is my contention that we miss out on the beauty and efficiency of the language if we do We miss out on the ability to learn about the ins and outs of the language In this book, we shall deliberately be using the breadth of the Object Pascal language in Delphi I’m not concerned that Java... bunch of strings, and then setting the Sorted property to true to get them in order) “OK,” I hear you say, “writing about algorithms is fine, but why bother with Delphi or Kylix?” By the way, let’s set a convention early on; otherwise I shall be writing the phrase Delphi or Kylix” an awful lot When I say Delphi, ” I really mean either Delphi or Kylix Kylix was, after all, known for much of its pre-release... present them in what might be termed historical order, the order of their influence on me The first two are a couple of gentlemen I’ve never met or spoken to, and yet who managed to open my eyes to and kindle my enthusiasm for the world of algorithms If they hadn’t, who knows where I might be now and what I might be doing I’m speaking of Donald Knuth (http://www-cs-staff.stanford edu/~knuth/) and Robert... make 12, put the 2 under the units column, and then carry 1 above the 4 1 45 17 + 2 AM FL Y You’d then add the carried 1, the 4 and the other 1 to make 6, which you’d then write underneath the tens column And, you’d have arrived at the concentrated answer: 62 TE Notice that what you had been taught was an algorithm to perform this and any similar addition You were not taught how to add 45 and 17 specifically . Team-Fly ® The Tomes of Delphi ™ Algorithms and Data Structures Julian Bucknall Wordware Publishing, Inc. Library of Congress Cataloging-in-Publication Data Bucknall, Julian Tomes of Delphi: algorithms. efficiency of algorithms, starting out with the big-Oh notation, continuing with timing of the actual run time of algo - rithms, and finishing with the use of profilers. We shall discuss data representation. on the beauty and efficiency of the language if we do. We miss out on the ability to learn about the ins and outs of the language. In this book, we shall deliber - ately be using the breadth of