Mastering Algorithms with Perl phần 10 pot

authentication and integrity, 533-537discarding invalid winnowing, 558hiding steganography, 555-558passwords, authorizing, 528-533 smoothing, 648 data encryption see encryption Data Encr

access methods, 526

authentication and integrity, 533-537discarding invalid (winnowing), 558hiding (steganography), 555-558

passwords, authorizing, 528-533

smoothing, 648

data encryption (see encryption)

Data Encryption Standard (see DES)

data link escape (DLE) character, 414

tracking both ends, 52-55

lookup searching and, 159, 173

matrices (see matrices)

sets (see sets)

traversal performance, 72

union-tree forests, 326

within arrays, 37-45

dataflow analysis, 396

Date: :Calc module, 489

Date: :Convert module, 490

Date: :GetDate module, 490

Date: :Manip module, 489

dates and times, 489

binary tree elements, 77, 80-81, 84

graph edges and vertices, 297-299

linked list elements, 55, 60

set members (subtracting), 205, 218

DES (Data Encryption Standard), 528, 543

Perl implementation (SSLeay), 543

DES-EDE and DES-EDE3 encryption algorithms, 543descendant vertices, 315

destroy( ) (double package), 66, 68

difference levels (Wu-Manber), 382

differences and fuzzy matching, 379

directed acyclic graphs (DAGs), 304, 312single-source shortest paths, 338

directed graphs and edges, 277-279, 291-293directed( ), 292

direction, specifying, 433-435

directional alternative hypotheses, 612

directories, searching with B-trees, 169

discrete probability distributions, 575

algorithms for (list), 592-598

greatest common (see GCD)

DLE character, 414break

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Dominus, Mark-Jason, 71, 113, 171, 386, 416, 505

double package (example), 65

double-ended queues (deques), 40-42

circular linked lists vs., 60

double_head package, 68

doubly-linked lists, 65-71

downloading files, risks, 534

dynamic programming, 22, 202

matrix chain products, 269dynamic variables, 36

caching, 16

dynamic allocation, 37

floating-point numbers, 14heaps, 92

linked lists, 47

tail pointers, 54

list traversal performance, 72

of Perl source code, 562-564

product development (government restrictions), 527public key, 533, 543, 548-554

winnowing and chaffing, 558-562

(see also cryptography)

encryption object, creating, 546

English stemming (see stemming)

epsilon, 472

eq statement, 359break

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equations, solving, 634-642

approximating roots, 638-640

multiple nonlinear equations, 640-642

quadratics and cubics, 635-638

Eratosthenes, sieve of, 504

shift-OR exact matching, 377-379

exclusive binary or (XOR) operator, 220-221

exclusive logical or (xor) operator, 210

exclusive-or (XOR), 538, 540

exhaustive search, 180-185

factoring large numbers, 549

false hits (string matching), 357, 365

feedback methods (encryption), 543

B-trees to search for, 169

content changes, detecting, 526

downloading, security risks, 534

encrypting/decrypting entire, 547

mailing (security risks), 527

Filter module, 562

filtering Perl source code, 562

finding (see searching)

finite arithmetic, 510

finite automata, 395-396

deterministic vs nondeterministic, 396

fuzzy (approximate) matching, 353, 379, 388

Baeza-Yates-Gonnet shift-add algorithm, 379-382

Baeza-Yates-Gonnet shift-OR algorithm, 377

longest common subsequence (LCS), 386

regular expressions (String::Approx), 387

Wu-Manber k-differences algorithm, 382-387

(see also phonetic algorithms)

fuzzy sets, 241

exhaustive search, 180-185

game interface for, 176-180

killer move strategy, 189, 202

inclusion within polygons, 443-449intersections, 435-443

line intersection, 435-443

Manhattan intersections, 440-443trigonometry, 491

grading test results, 607

Graham's scan algorithm, 452-456

Graph: :Directed class, 278, 293, 299

Graph: :Kruskal class, 231, 352

Graph: :Undirected class, 278, 293, 299

(see also graphs)

graphical application development, 467

graphics, general references on, 650

graphics modules, 464-468

graphs, 273-352

attributes, 286, 299

classes and connectivity, 279-281, 296, 316-326biconnected graphs, 320-323

Traveling Salesman problem, 350

CPAN modules for, 351

edges (see vertices, graph)

general references on, 650

graphviz package, 301

great circle distance, 429

great_circle_distance( ), 429

greatest common divisor (see GCD)

greedy search algorithms, 195

avoiding searching with, 158

hashes of hashes (hohs), 29

hashes of lists (hols), 29, 118

Huffman encoding, 417

inserting and deleting elements, 55

binary search and, 164

lists of hashes (lohs), 29break

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(cont'd)

hashes

lists of lists (lols), 29

lookup searching and, 174

Heap: :Binary module, 99

Heap: :Binomial module, 99

Heap: :Fibonacci module, 99

heapdown( ), 95-99

heapdump( ) (Heap modules), 101

branch and bound method, 196

caching prime numbers, 505

efficiency of, 92

finding maximum/minimum, 122-125Heap modules, 99

hohs (hashes of hashes), 29

hols (hashes of lists), 29

reversing element order, 118

Horner's rule, 363

Howland, Gary, 568

HP program 183

images, secret messages in, 555

imaginary (complex) numbers, 485

implementations of algorithms, 6

in_degree( ), 297

in-degree, vertex, 279

in site (in place) sorting, 119

inclusion within polygons, 443-449

incremental sum (Rabin-Karp), 365

individuals using cryptography, 527

infinite discrete distributions, 590-591

iterative vs recursive algorithms, 21

J

jacobian( ), 630, 640

Jacobian matrix, 629-631, 640

Janus heaps, 99

joining binary trees, 85-86

junk messages, adding (chaffing), 558

K

k-connected graphs, 286, 320

keys, encryption, 540, 542

converting from hex to bytes, 548

interchanging public and private, 552lost or stolen, 564

Laplace distribution, 596

laplace_expected( ), 596

laplace_variance( ), 596

last occurrence heuristic, 373

LCM (least common multiple), 504lcm( ), 504

LCS (longest common subsequence), 386ldump( ) (double_head), 70

leaf vertices, 312

least common multiple (LCM), 504legal issues (cryptography), 526-527Lehman, Marc, 465

linear combination theorem, 500

linear congruential generators, 567linear least squares method, 622

linear search, 161

linear_solve( ), 643

linear_string( ), 161break

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lines, fitting to data, 622-624

lines, searching for multiple, 362

Lingua: :EN: :Inflect module, 393

Lingua: :PT: :Conjugate module, 393

links (see edges, graph; graphs)

list iterators (Set: :IntSpan), 230

lists (see arrays; hashes)

literal( ), 399

loaded dice, 582-589

local statement, 36

locales and sorting, 113-114

location of variables (see references)

logical and (&&) operator, 240

logical exclusive or (xor) operator, 210logical not (!) operator, 240

logical or ( | | ) operator, 210, 240

lognormal( ), 597

lognormal_expected( ), 597

lognormal_variance( ), 597

lohs (list of hashes), 29

lols (lists of lists), 29, 34

binary search in list, 162-165

binary search in tree, 167-171

Marquess, Paul, 117, 170, 423, 562match heuristic, 373

matching strings (see regular expressions)Math modules

Math: :BigFloat module, 477-480Math: :BigInt module, 363, 477-480random BigInts, 579-581

Math: :Complex module, 485, 635Math: :Fraction module, 480

Math: :Matrix module, 245, 641Math: :MatrixBool module, 231Math: :MatrixReal module, 245adding constants to matrices, 248

adding matrices together, 251

Math: :Trig module, 429, 491

Math: :TrulyRandom module, 568

chain products, 269-272rotating, 258

minimum cost spanning tree, 185

minimum spanning trees (MSTs), 326-332Kruskal's algorithm, 326-329, 352

Monty Hall problem, 590

move object (game interface), 177

multibyte character matching, 360

multibyte character sorting, 107break

LCM (least common multiple), 504multiplication (*) operator, 257

multiplying matrices together, 256-258chain products, 269-272

National Security Agency (NSA)

strong encryption, controlling use, 527natural numbers, 469

none, probability of, 569-570

nongame dynamic searches, 193-202

normal (Gaussian) distribution, 566, 591, 595normalization, 582

normalize( ), 601

not (!) operator, 240

NP-complete, NP-hard problems, 184

dates and times, 489

factorials of fractional numbers, 15

derivatives and integrals, 627-634

interpolation, extrapolation, curve fitting, 642-648solving equations, 634-642

probability (see probability)

random (see random numbers)

odd perfect numbers, 523

OFB (Output Feedback), 543

offset (pattern shift), 357

opening book strategy, 192

operating systems and data access, 527operator precedence (priority), 397optimization (see efficiency of algorithms)optimizing parse trees, 396

order of growth values, 17-20

ordering (see sorting)

Parse: :Lex module, 406

Parse: :RecDescent module, 407

partial ordering (graphs), 304

partition( ), 137-140

Baeza-Yates-Gonnet shift-add algorithm, 379-382Baeza-Yates-Gonnet shift-OR algorithm, 377longest common subsequence (LCS), 386

regular expressions (String: :Approx), 387

Wu-Manber k-differences algorithm, 382-387phonetic algorithms, 388-389

metaphone algorithm (Text: :Metaphone), 389soundex algorithm (Text: :Soundex), 388-389Rabin-Karp algorithm

binary mask, 368

regular expressions (see regular expressions)

stemming and inflection, 389-393

Lingua: :EN: :Inflect module, 393

Lingua: :PT: :Conjugate module, 393

Text: :German module, 393

Text: :Stem module, 392

manipulating matrix elements, 246

matrix chain products, 269

metaphone algorithm (Text: :Metaphone), 389

soundex algorithm (Text: :Soundex), 388-389

pluralizing English words, 393

Point class (example), 26

point_in_quadrangle( ), 448

point_in_triangle( ), 446

points

closest pair of, 457-464

directives at, computing, 628-629

fitting polynomials to, 643

approximating roots, 638-640fitting to points, 643

solving for roots, 634-642pop operator, 38, 40

population variance estimation, 614Portuguese verb conjugation, 393position object (game interface), 176positive correlation, 620, 624

positive lookahead assertion, 356POSIX module, 473-474

postorder vertex processing, 314pow( ), 479

Pretty Good Privacy (PGP), 565

prev( ) (double package), 66

permutations and combinations, 571-574random numbers, 567-568

(see also statistics)

productions (of tokens), 396

profiling, 38

programs

passwords for (see passwords)

in this book, obtaining, xv

progressions of numbers, 492-498

proper string prefixes/suffixes, 357

proportional_binary_string_search( ), 166proportional search, 165-167

El Gamal key, generating, 552

generating prime numbers, 549

generator seed, 567-568

improving randomness, 568

(see also probability distributions)

random values (prepending to passwords), 532

random variables, 574

randomized running time, 140

randomizing the pivot choice, 140

rand( ) function, 540break

tracking both ends, 52-55

reformulating the problem, 22

regression line, 622

regular expressions, 354-357

positive/negative lookahead assertions, 356repetition quantifiers, 356

tips and tricks, 355

removing (see deleting)

rendering graphs (see graphs, displaying)

RSA public key encryption, 549-552run-length encoding (RLE), 228, 412-415rvals( ), 253

S

s/// substitution operator, 357, 399saddle( ), 642

graph traversal, 309, 314

efficiency, 157, 172-175

external searches, 174

generative searching, 158, 175-202

exhaustive search, 180-185

game interface for, 176-180

killer move strategy, 189, 202

linked list contents, 56

for list maxima/minima, 122-125

lookup searches 158-175

binary search in list, 2-5, 162-165, 389

binary search in tree, 167-171

security (see cryptography)

seed for random number generation, 567-568

seek( ), 8

CPAN modules for, 227-232

Bit: :Vector module, 227, 230

Set: :Bag module, 241

Set: :IntegerFast module, 231

Set: :IntRange module, 227, 232

Set: :IntSpan module, 227-228, 242

Set: :Object module, 227-228

queue order (FIFO), 38

radix sorts, 145-147

in reverse (see reverse order)

Schwartzian Transform, 109-113

Sort: :ArbBiLex module, 114

Sort: :Fields module, 106

Sort: :Versions module, 106

stability and sensitivity, 119

stack order (LIFO), 39

topological sort, 304-307, 309

sos_as_string( ), 234

soundex algorithm, 388-389

source code, encrypted, 562-564

source vertex (flow network), 279, 345source_vertices( ), 297

space (see disk space)

space characters, hiding messages with, 557space in regular expressions, 355

spaceship (<=>) operator, 105

Spafford, Eugene, 536

sparse graphs, 286

sparse sets, 229

speaking secret messages, 555

speed (see efficiency of algorithms)

fitting lines to data, 622-624

general references on, 651

Lingua: :EN: :Inflect module, 393

Lingua: :PT: :Conjugate module, 393

Text: :German module, 393

Text: :Stem module, 392

straight radix sort, 145break

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street addresses, data structures for, 27, 31

string( ), 399-400

String: :Approx module, 387

String: :ShellQuote module, 410

run-length encoding (RLE), 412-415

converting data into, 299

general references on, 650

matching algorithms, 353-424

approximate (fuzzy) matching, 353, 377, 379, 387Baeza-Yates-Gonnet shift-OR algorithm, 377-379Boyer-Moore algorithm, 373-375

Boyer-Moore-Horspool algorithm, 375

exact matching, 354

Knuth-Morris-Pratt algorithm, 370-372, 395nạve matching, 357-362

sorting (see sorting)

subroutines (see algorithms)

subscripts, array and hash elements, 26, 29subsets, 223

tabs, hiding messages in, 557

tail pointer (linked lists), 52

text (see strings)

Text: :Abbrev module, 408

Text: :Balanced, 410

Text: :DelimMatch module, 409

Text: :German module, 393

Text: :Metaphone module, 389

Text: :ParseWords module, 409

Text: :Soundex module, 388-389Text: :Stem module, 392

three-dimensional modeling, 466break

Time: :CTime module, 490

Time: :Date module, 490

Time: :DaysInMonth module, 490

Time: :JulianDay module, 490

time measurement (uniform distributions), 578

Time: :ParseDate module, 490

time resources, 9-11

Time: :Timezone module, 490

times and dates, 489

timestamp, hiding messages in, 557

top-down programming strategy, 22

topological sort, 304-307, 309

total degree, 280

total sum (Rabin-Karp) 365

trailing spaces, hiding messages with, 557transformation matrices, 257

transitive closure, 342-344

TransitiveClosure_Floyd_Warshall( ), 344translation, 405

true hits (string matching), 357

TSP (Traveling Salesman problem), 184, 350t-test, 614-616

underscores and numeric comparison, 107

undirected graphs and edges, 277-279, 291-293, 317Unicode standard, 107, 651

bit vectors for, 216

use constant statement, 48

use integer statement, 14, 470

use locale statement, 106

''Useless use of in void context" warning, 13

usernames and matching passwords, 528

/usr/dict/words file, 6-8

V

validate( ) (Heap modules), 101

validating data (checksums), 534-537

validation keys (winnowing and chaffing), 558

verifying passwords (Perl program), 528

versioncmp( ) (Sort: :Versions), 107

versions( ) (Sort: :Versions), 107

versions of Perl, xiv

leaves and branches, 312

parents, children, ancestors, descendants, 315predecessor, successor, neighbor, 315

sink and source vertices, 345

vertex sets, 326

weight/cost, 329

(see also graphs)

very big/small numbers, 477-480, 574

weight, graph edges, 286, 334

weight, graph vertices, 329

/x regular expression modifier, 355

XOR (binary exclusive or) operator, 220-221, 538

xor (exclusive logical or) operator, 210

About the Authors

Jon Orwant is president of Readable Publications, Inc He founded The Perl Journal in 1995

and served as the sole editor, publisher, accountant, designer, and postal antagonizer until

1999 He has been on the technical committee of all of O'Reilly' s Perl conferences (where he

is the emcee of the Internet Quiz Show), and he speaks frequently about Perl, most recently atthe first YAPC on Rebuilding Post-Apocalyptic Civilization with Perl

He is currently an MIT Media Laboratory IBM Fellow, creating programs that create programsthat play games His other research interests are user modeling and electronic publishing Hegives frequent talks about Media Lab research, most recently on the promise and perils ofInternet gambling

In 1993, he created the world's first Internet stock-picking game His Markovmodel basedRock-Paper-Scissors program has been undefeated since 1997 He also performs professionalvoice-overs A court injunction from the Commonwealth of Massachusetts prohibits him fromcooking or otherwise assisting in the preparation of any foodstuff meant for human

consumption

Jarkko Hietaniemi is the creator and Master Librarian of CPAN: Comprehensive Perl

Archive Network He has also been known to frequent Perl developer forums Luckily enough,getting his M.S in Computer Science in the field of parallel computing didn't interfere overlymuch with his Perl and Unix hacking During those savored moments of offline time, he fanciesgobbling up speculative fiction and popular science His real life employer is Nokia ResearchCenter

John Macdonald has been using Perl commercially since 1988 for a suite of Unix system

administration tools His background with Unix dates back to the days when Unix was written

in PDP-11 assembler and later includes representing the University of Waterloo at the firstUnix Users Meeting at City University of New York in the mid-1970s while finishing his M.Math degree (In those days before the creation of Usenix, the people at the meeting would sittogether around a single table.) In addition, his background includes work on compilers, kernelinternals, device drivers, and the like He has also been observed partaking in recreationalcomputing activities

Colophon

The animal on the cover of Mastering Algorithms with Perl is a wolf (Canis lupus) The wolf,

a member of the dog family, is one of the most sociable of mammals Wolves live and hunt inpacks, which consist of one pair of alpha male and female wolves and several offspring Packsize is usually five to nine wolves Each wolfcontinue

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pack has its own territory, which they will mark and fight to defend Wolves often travel long