The "pearls" in question center not only on choosing the right algorithms (like binary searches, sorting techniques, or sparse arrays) but also on showing how to solve problems effectively. Each chapter frames a particular programming task--such as sorting numbers, creating anagrams, or counting the words in a block of text--many drawn from Bentley's experiences in his long career as a developer. The book traces the process of arriving at a fast, efficient, and accurate solution, along with code profiling to discover what works best. After refining the correct answer, each chapter enumerates programming principles that you can use on your own.

The author also challenges you to think like an engineer, and each chapter ends with about a dozen problems to get you thinking creatively about design issues. (Sidebars on such historical topics as the first computer solutions to computer chess, spell-checking, and even architectural design help create a perspective on successful problem solving and make for a truly educational and enjoyable tour of how to become a better programmer.) Bentley also asks the reader to think analytically about the world with "back of the envelope" estimation techniques drawn from engineering. Appendices list the algorithms and code rules covered in the book, plus some sample solutions.

Fans of the first edition of this title will be pleased to see this favorite computer text brought up to date for today's faster hardware. Whether you want to improve your command of algorithms or test your problem-solving skills, the new version of Programming Pearl is a challenging, instructive, and thoroughly entertaining resource. --Richard Dragan

Topics covered: Programming and problem-solving tutorial, sorting algorithms, merge sort, bit vectors, binary searches, program correctness and testing, improving performance, engineering and problem-solving techniques, performance estimates, designing for safety, divide-and-conquer and scanning algorithms, tuning code, tips for more efficient memory usage, insertion sort, quicksort algorithms, sparse arrays, searching algorithms, binary search trees, heaps, priority queues, searching text, and generating random text.

Computer programming has many faces. Fred Brooks paints the big picture in

The Mythical Man Month; his essays underscore the crucial role of management

in large software projects. At a finer grain, Steve McConnell teaches good programming

style in Code Complete. The topics in those books are the key to good software

and the hallmark of the professional programmer. Unfortunately, though, the

workmanlike application of those sound engineering principles isn't always thrilling

-- until the software is completed on time and works without surprise.

About the Book
The columns in this book are about a more glamorous aspect of the profession:

programming pearls whose origins lie beyond solid engineering, in the realm

of insight and creativity. Just as natural pearls grow from grains of sand that

have irritated oysters, these programming pearls have grown from real problems

that have irritated real programmers. The programs are fun, and they teach important

programming techniques and fundamental design principles.

Most of these essays originally appeared in my ''Programming Pearls'' column

in Communications of the Association for Computing Machinery. They were

collected, revised and published as the first edition of this book in 1986.

Twelve of the thirteen pieces in the first edition have been edited substantially

for this edition, and three new columns have been added.

The only background the book assumes is programming experience in a high-level

language. Advanced techniques (such as templates in C++) show up now and then,

but the reader unfamiliar with such topics will be able to skip to the next

section with impunity.

Although each column may be read by itself, there is a logical grouping to

the complete set. Columns 1 through 5 form Part I of the book. They review programming

fundamentals: problem definition, algorithms, data structures and program verification

and testing. Part II is built around the theme of efficiency, which is sometimes

important in itself and is always a fine springboard into interesting programming

problems. Part III applies those techniques to several substantial problems

in sorting, searching and strings.

One hint about reading the essays: don't go too fast. Read them carefully,

one per sitting. Try the problems as they are posed -- some of them look easy

until you've butted your head against them for an hour or two. Afterwards, work

hard on the problems at the end of each column: most of what you learn from

this book will come out the end of your pencil as you scribble down your solutions.

If possible, discuss your ideas with friends and colleagues before peeking at

the hints and solutions in the back of the book. The further reading at the

end of each chapter isn't intended as a scholarly reference list; I've recommended

some good books that are an important part of my personal library.

This book is written for programmers. I hope that the problems, hints, solutions,

and further reading make it useful for individuals. The book has been used in

classes including Algorithms, Program Verification and Software Engineering.

The catalog of algorithms in Appendix 1 is a reference for practicing programmers,

and also shows how the book can be integrated into classes on algorithms and

data structures.

The Code
The pseudocode programs in the first edition of the book were all implemented,

but I was the only person to see the real code. For this edition, I have rewritten

all the old programs and written about the same amount of new code. The programs

are available at this book's web site. The code includes much of the scaffolding

for testing, debugging and timing the functions. The site also contains other

relevant material. Because so much software is now available online, a new theme

in this edition is how to evaluate and use software components.

The programs use a terse coding style: short variable names, few blank lines,

and little or no error checking. This is inappropriate in large software projects,

but it is useful to convey the key ideas of algorithms. Solution 5.1 gives more

background on this style. The text includes a few real C and C++ programs, but

most functions are expressed in a pseudocode that takes less space and avoids

inelegant syntax. The notation for i = 0, n) iterates i from

0 through n-1. In these for loops, left and right parentheses denote

open ranges (which do not include the end values), and left and right square

brackets denote closed ranges (which do include the end values). The phrase

function(i, j) still calls a function with parameters i and j,

and arrayi, j still accesses an array element.

This edition reports the run times of many programs on ''my computer'', a 400MHz

Pentium II with 128 megabytes of RAM running Windows NT 4.0. I timed the programs

on several other machines, and the book reports the few substantial differences

that I observed. All experiments used the highest available level of compiler

optimization. I encourage you to time the programs on your machine; I bet that

you'll find similar ratios of run times.

To Readers of the First Edition
I hope that your first response as you thumb through this edition of the book

is, ''This sure looks familiar.'' A few minutes later, I hope that you'll observe,

''I've never seen that before.''

This version has the same focus as the first edition, but is set in a larger

context. Computing has grown substantially in important areas such as databases,

networking and user interfaces. Most programmers should be familiar users of

such technologies. At the center of each of those areas, though, is a hard core

of programming problems. Those programs remain the theme of this book. This

edition of the book is a slightly larger fish in a much larger pond.

One section from old Column 4 on implementing binary search grew into new Column

5 on testing, debugging and timing. Old Column 11 grew and split into new Columns

12 (on the original problem) and 13 (on set representations). Old Column 13

described a spelling checker that ran in a 64-kilobyte address space; it has

been deleted, but its heart lives on in Section 13.8. New Column 15 is about

string problems. Many sections have been inserted into the old columns, and

other sections were deleted along the way. With new problems, new solutions,

and four new appendices, this edition of the book is 25 percent longer.

Many of the old case studies in this edition are unchanged, for their historical

interest. A few old stories have been recast in modern terms.

Acknowledgments for the First Edition
I am grateful for much support from many people. The idea for a Communications

of the ACM column was originally conceived by Peter Denning and Stuart Lynn.

Peter worked diligently within ACM to make the column possible and recruited

me for the job. ACM Headquarters staff, particularly Roz Steier and Nancy Adriance,

have been very supportive as these columns were published in their original

form. I am especially indebted to the ACM for encouraging publication of the

columns in their present form, and to the many CACM readers who made

this expanded version necessary and possible by their comments on the original

columns.

Al Aho, Peter Denning, Mike Garey, David Johnson, Brian Kernighan, John Linderman,

Doug McIlroy and Don Stanat have all read each column with great care, often

under extreme time pressure. I am also grateful for the particularly helpful

comments of Henry Baird, Bill Cleveland, David Gries, Eric Grosse, Lynn Jelinski,

Steve Johnson, Bob Melville, Bob Martin, Arno Penzias, Marilyn Roper, Chris

Van Wyk, Vic Vyssotsky and Pamela Zave. Al Aho, Andrew Hume, Brian Kernighan,

Ravi Sethi, Laura Skinger and Bjarne Stroustrup provided invaluable help in

bookmaking, and West Point cadets in EF 485 field tested the penultimate draft

of the manuscript. Thanks, all.

Acknowledgments for the Second Edition
Dan Bentley, Russ Cox, Brian Kernighan, Mark Kernighan, John Linderman, Steve

McConnell, Doug McIlroy, Rob Pike, Howard Trickey and Chris Van Wyk have all

read this edition with great care. I am also grateful for the particularly helpful

comments of Paul Abrahams, Glenda Childress, Eric Grosse, Ann Martin, Peter

McIlroy, Peter Memishian, Sundar Narasimhan, Lisa Ricker, Dennis Ritchie, Ravi

Sethi, Carol Smith, Tom Szymanski and Kentaro Toyama. I thank Peter Gordon and

his colleagues at Addison-Wesley for their help in preparing this edition.

0201657880P04062001