README.md

UVa Problems by OnlineJudge

Introduction

Getting Started: The Easy Problems

Super Easy

• TEX Quotes url
• Celebrity jeopardy url
• Combination Lock url
• Searching for Nessy url
• Relational Operator* url
• Parking url
• Division of Nlogonia* url
• Automatic Answer url
• Cost Cutting* url
• Language Detection url
• Emoogle Balance url
• One-Two-Three url
• Packing for Holiday url
• Save Setu url
• Hajj-e-Akbar url

Easy

• Secret Research url
• Loansome Car Buyer* url
• Ecological Premium url
• The Swallowing Ground url
• Summing Digits url
• Event Planning* url
• Sub-prime url
• Jumping Mario url
• Horror Dash* url
• Lumberjack Sequencing url
• Google is Feeling Lucky url
• Tariff Plan url
• Zapping url
• Robot Instructions url
• A Special "Happy Birthday" Song!!! url

Medium

• Greedy Gift Givers url
• The Snail* url
• Blowing Fuses url
• Request for Proposal* url
• Zeros and Ones url
• Love Calculator url
• Prerequisites? url
• Bender B. Rodríguez Problem* url
• Train Tracks url
• Burger Time? url
• Laser Sculpture url
• Digits url
• Brainfuck url
• Hardest Problem Ever (Easy) url

Ad Hoc Problems - Part 1

Game (Card)

• Beggar My Neighbour url
• Bridge Hand Evaluator* url
• Bridge Hands url
• Stack 'em Up url
• Poker Hands url
• What is the Card?* url
• Tarot scores. url
• Cards' Exchange url
• Jollo* url

Game (Chess)

• Correct Move url
• Chess* url
• How Many Knights* url
• Check The Check url
• Chessboard in FEN* url
• Move the bishop url
• Queen url

Game (Others), Easier

• Master-Mind Hints url
• Hangman Judge* url
• Master Mind Helper url
• Minesweeper* url
• Mine Sweeper url
• Die Game url
• Guessing Game url
• Snakes and Ladders* url
• Bingo! url

Game (Others), Harder

• Simulation Wizardry url
• The Spot Game url
• Othello url
• Puzzle url
• Crossword Answers url
• SameGame Simulation url
• Hi-Q url
• Bowling* url
• Chutes and Ladders url
• Tic Tac Toe url
• Rock, Scissors, Paper* url
• Traditional BINGO* url
• Rock-Paper-Scissors Tournament url

Palindrome

• Pesky Palindromes url
• Palindromes* url
• Reverse and Add url
• Mother bear* url
• Magic square palindromes.* url
• Counting Chaos url

Anagram

• Anagram checker url
• Ananagrams* url
• Anagram* url
• Anagrams* url
• Anagrams (II) url
• Word Amalgamation url
• Generating Fast url

Interesting Real Life Problems, Easier

• Traffic Lights* url
• Transaction Processing url
• 18,000 Seconds Remaining url
• Booklet Printing* url
• Quantiser url
• WERTYU url
• Longest Nap url
• Major Scales url
• Calories from Fat url
• Beat the Spread!* url
• SMS Typing url
• Financial Management url
• A Change in Thermal Unit url
• Jingle Composing url
• Baby Me url

Interesting Real Life Problems, Harder

• Telephone Tangles url
• Gondwanaland Telecom url
• Recognizing Good ISBNs url
• Getting Chorded url
• Postscript* url
• Population Explosion url
• OOPS! url
• Majoring in Scales url
• Linear Cellular Automata url
• Balancing Bank Accounts url
• Counterfeit Dollar* url
• LC-Display url
• Consanguine Calculations* url
• Eb Alto Saxophone Player url
• Fitting Text into Slides url
• O: dah dah dah! url
• Credit Check url
• Tax Calculator url

Ad Hoc Problems - Part 2

Time

• Clock Patience url
• Maya Calendar url
• Clock Hands* url
• Y3K Problem* url
• Leap Year or Not Leap Year and ... url
• Watching Watches url
• Time Zones url
• The decadary watch url
• How old are you? url
• Dates url
• Mirror Clock url
• Alarm Clock url
• Cancer or Scorpio* url
• Coming Home url
• Doom's Day Algorithm url
• Schedule of a Married Man url
• Electricity url
• February 29 url
• Hours and Minutes url

'Time Waster' Problems

• Student Grants url
• Code Generation url
• Processing MX Records url
• Interpreting Control Sequences url
• Transferable Voting (II) url
• Making the Grade url
• Message Routing url
• Amazing* url
• Parking Lot url
• Shark url
• Loading a Cargo Ship url
• Interpreter url
• AutoFish url
• Australian Voting url
• Automated Judge Script url
• Graphical Editor url
• Chasing After Don Giovanni url
• Little Ali's Little Brother! url
• Energy Saving Microcontroller url
• All Integer Average* url
• Mobile Casanova* url
• Garbage Collection url

Data Structures and Libraries

Linear Data Structures with Built-in Libraries

1D Array Manipulation

• Borrowers url
• Mapmaker url
• Machined Surfaces url
• Synching Signals url
• Permutation Arrays url
• Box of Bricks url
• False coin url
• 487--3279 url
• Jolly Jumpers* url
• Hartals url
• Soundex url
• Let's Play Magic! url
• Just Finish it up url
• Group Reverse url
• Only I did it! url
• Newspaper* url
• Musical Loop url
• No Problem url
• Alaska url
• Pole Position url
• Army Buddies* url

2D Array Manipulation

• The Blocks Problem url
• Matty's Blocks url
• Mirror, Mirror url
• Error Correction url
• Flip-Flop the Squarelotron url
• Free spots url
• Rotated square* url
• Spiral Tap* url
• Add bricks in the wall url
• Symmetric Matrix url
• Have Fun with Matrices url
• Grid Successors* url
• Formula 1 url
• Brothers url
• Polyomino Composer url
• NumPuzz I url

C++ STL algorithm (Java Collections)

• Searching Quickly url
• ID Codes* url
• Unix ls url
• Little Black Book url
• Head Judge Headache url
• Lunch in Grid City url
• Wordfish url
• A mid-summer night's dream. url
• What is the Median?* url
• Football (aka Soccer) url
• Contest Scoreboard* url
• Football Sort url
• Colin and Ryan url
• Children's Game url
• Building designing url
• Sort! Sort!! and Sort!!! url
• Image Coding url
• Automate the Grades url
• A Minimum Land Price url
• Birthdates url

Bit Manipulation

• One Little, Two Little, Three Little Endians url
• Date Bugs url
• Jollybee Tournament url
• The Most Potent Corner* url
• Grey Codes url
• Brother Arif, Please feed us! url
• Multitasking* url
• Splitting Numbers* url

C++ STL list (Java LinkedList)

• Broken Keyboard (a.k.a. Beiju Text)* url

C++ STL stack (Java Stack)

• "Accordian" Patience url
• Rails* url
• Anagrams by Stack* url
• Containers* url
• Unique Factorization url

C++ STL queue and deque (Java Queue and Deque)

• Team Queue url
• The Lonesome Cargo Distributor* url
• Ferry Loading III* url
• Throwing cards away I url
• Ferry Loading IV* url
• Printer Queue url
• That is Your Queue url

Non Linear Data Structures with Built-in Libraries

C++ STL map (Java TreeMap)

• Word Index url
• The Department of Redundancy Department url
• Entropy Text Analyzer url
• Genes url
• File Fragmentation url
• CDVII url
• Hardwood Species* url
• Babelfish url
• Hay Points url
• SQF Problems url
• Open Source url
• Conformity* url
• Bankrupt Baker url
• Exhibition url
• Unique Snowflakes* url
• Ballot evaluation url
• Document Analyzer url
• Do Your Own Homework url
• Updating a Dictionary url
• Slogan Learning of Princess url

C++ STL set (Java TreeSet)

• Black Box url
• Lemmings Battle!* url
• Andy's First Dictionary url
• Andy's Second Dictionary url
• Hoax or what* url
• CD* url
• Just Prune The List url

C++ STL priority_queue (Java PriorityQueue)

• Argus* url
• Add All* url
• I Can Guess the Data Structure!* url

Data Structures with Our-Own Libraries

Graph Data Structures Problems

• The Forrest for the Trees* url
• Matrix Transpose* url
• My Dear Neighbours url
• Demanding Dilemma url
• Easy Problem from Rujia Liu?* url

Union-Find Disjoint Sets

• Network Connections* url
• The Suspects url
• War url
• Forests url
• Waking up brain* url
• Ubiquitous Religions url
• Friends url
• Nature url
• Virtual Friends* url
• Money Matters url

Tree-related Data Structures

• Quadtrees url
• SKYLINE url
• Frequent values* url
• Census url
• Stern-Brocot Tree url
• Ahoy, Pirates!* url
• Potentiometers url
• Interval Product* url

Problem Solving Paradigms

Complete Search

Iterative (One Loop, Linear Scan)

• Ecological Bin Packing url
• Quirksome Squares url
• Integer Sequences from Addition of Terms* url
• Expert Enough?* url
• Fractions Again?!* url
• Necklace url
• Open Credit System url

Iterative (Two Nested Loops)

• The Skyline Problem url
• Run url
• Magic Numbers url
• Nonstop Travel url
• Division url
• Sales* url
• Vito's Family url
• Closest Sums* url
• Antiarithmetic? url
• Tour de France* url
• Start Grid url
• Memory Overflow url

Iterative (Three or More Nested Loops, Easier)

• Recycling url
• Perfect Hash url
• Lotto* url
• Ecosystem url
• Triple Ties: The Organizer's Nightmare url
• Dart-a-Mania* url
• The path in the colored field* url
• Counting Rectangles url
• The Wedding url
• Largest Square url
• Maximum Product url
• Tele-loto url
• Ant's Shopping Mall url
• Movie Police url

Iterative (Three or More Nested Loops, Harder)

• Cube painting url
• Safebreaker url
• Perfect Cubes url
• Sumsets url
• (2/3/4)-D Sqr/Rects/Cubes/Boxes? url
• Rat Attack url
• Blocks url
• The Sum Equals the Product url
• Citizen attention offices* url
• Triangle Counting url
• Tautology url
• Grocery store* url
• Three-square url
• Blackboard Bonanza url
• Simple Equations* url
• Argentina url
• Dice url

Iterative (Fancy Techniques)

• Bandwidth url
• Switching Channels url
• Block Voting url
• Don't Get Rooked url
• Zones* url
• Network url
• The broken pedometer url
• Dig the Holes url
• Grid Game* url
• Social Constraints url
• Overlapping Scenes url
• Water Gate Management url
• Fun Coloring url
• Help Dexter url
• Bars* url

Recursive Backtracking (Easy)

• The Sultan's Successors url
• Call Forwarding url
• The Settlers of Catan url
• CD* url
• Passwords url
• All Walks of length "n" from the first node url
• The Hamming Distance Problem url
• 8 Queens Chess Problem url
• Hanoi Tower Troubles Again! url
• 23 out of 5 url
• Marcus url
• Y2K Accounting Bug* url
• Back to the 8-Queens* url

Recursive Backtracking (Medium)

• Budget Travel url
• Transportation url
• Mapping the Swaps url
• Boggle Blitz url
• Prime Ring Problem* url
• Jugs url
• Sum It Up* url
• Bundling Newspapers url
• Hamiltonian Cycle url
• Garden of Eden url
• Knuth's Permutation url
• Find the Permuted String url
• Help the Leaders url
• The dominoes solitaire* url
• The Ouroboros problem url
• Bad Code url
• The problem of the crazy linguist url
• DNA url

Recursive Backtracking (Harder)

• Krypton Factor url
• Stamps url
• Graph Coloring* url
• Firetruck url
• LED Test* url
• Bank (Not Quite O.C.R.) url
• Pizza Anyone? url
• Little Bishops url
• Numerical Maze url
• Password* url
• Place the Guards url
• Queue url
• ASCII Labyrinth url
• Going in Cycle!! url

Dynamic Programming

Max 1D Range Sum

• Jill Rides Again url
• Maximum Sub-sequence Product* url
• The jackpot* url
• Garbage Heap* url

Max 2D Range Sum

• Maximum Sum* url
• Largest Submatrix url
• Localized Summing for Blurring url
• Take the Land url
• Largest Block url
• Maximum sum on a torus* url
• Area* url

Longest Increasing Subsequence (LIS)

• History Grading url
• Testing the CATCHER url
• The Tower of Babylon url
• What Goes Up* url
• Strategic Defense Initiative url
• Tiling Up Blocks url
• Is Bigger Smarter? url
• Wavio Sequence url
• Nested Dolls url
• Trainsorting* url
• Murcia's Skyline* url

0-1 Knapsack (Subset Sum)

• Dividing coins url
• Diving for Gold url
• Sum of Different Primes url
• SuperSale url
• Ferry Loading url
• Divisible Group Sums* url
• Luggage url
• Trouble of 13-Dots* url
• Boxes url
• Term Strategy url
• Let's Yum Cha!* url
• Best Coalitions url

Coin Change (CC)

• Dollars url
• Making Change url
• Let Me Count The Ways* url
• Coin Change url
• e-Coins* url
• Pay the Price url
• Ingenuous Cubrency url
• Exact Change* url

Traveling Salesman Problem (TSP)

• Getting in Line* url
• Collecting Beepers* url
• Shopping Trip* url

Non Classical (The Easier Ones)

• Unidirectional TSP url
• Spreadsheet url
• String Popping url
• Cutting Sticks url
• Divisibility url
• Test the Rods url
• Flight Planner* url
• Game Show Math url
• The Marriage Interview :-) url
• Homer Simpson url
• Determine it url
• The Poor Giant url
• Bar Codes* url
• Marks Distribution url
• Simple Minded Hashing url
• How do you add?* url
• Lowest Price in Town url
• A Grouping Problem url
• Squares url
• Chest of Drawers url
• Wedding shopping url
• sqrt log sin url

Greedy

Classical, Usually Easier

• Station Balance url
• Radar Installation url
• Minimal coverage url
• Watering Grass url
• Coin Collector* url
• The Bus Driver Problem* url
• Gas Stations url
• Scarecrow* url

Involving Sorting (Or The Input Is Already Sorted)

• Shoemaker's Problem url
• Bridge url
• The Grand Dinner url
• Work Reduction url
• Foreign Exchange url
• The Mad Numerologist url
• The Trip, 2007* url
• WFF 'N PROOF url
• Setting Problems url
• Dragon of Loowater* url
• Shopaholic url
• Commando War url
• Boiled Eggs url
• A Match Making Problem* url
• Perfect Choir url

Non Classical, Usually Harder

• Packets url
• Parliament url
• ShellSort url
• All in All url
• Ferry Loading II url
• Editor Nottoobad url
• Maximum Sum (II)* url
• Marbles on a tree url
• Camel trading url
• Ants url
• Bit Mask* url
• Troublemakers url
• Wine trading in Gergovia url
• Dynamic Frog* url
• Annoying painting tool url
• Antimonotonicity url
• Discrete Pursuit url
• Fill the Square url
• Simple Adjacency Maximization url
• Moliu Number Generator url
• Short Story Competition url

Divide and Conquer

Binary Search

• Dropping Balls url
• Popes url
• The Stern-Brocot Number System url
• Where is the Marble? url
• Helping Fill Bates* url
• The Playboy Chimp url
• Number Sequence url
• The New Rule in Euphomia url
• Exact Sum* url
• Small Factors url
• Cantor url
• N + NOD (N) url
• Grapevine* url

Binary Search the Answer

• Solve It* url
• Fill the Containers* url
• Internal Rate of Return url
• Through the Desert url
• The Monkey and the Oiled Bamboo* url
• Electric Bill url

Other Divide and Conquer Problems

• Bit Maps* url

Graph

Graph Traversal

Just Graph Traversal

• Mutant Flatworld Explorers url
• Theseus and the Minotaur url
• Vertex url
• Domino Effect url
• Mapping the Route url
• Coast Tracker url
• Exchange Rates url
• Robot Motion url
• Maze Traversal url
• Monitoring the Amazon url
• Sticker Collector Robot* url
• Dominator url
• Knight in a War Grid* url
• As Long as I Learn, I Live url
• Forwarding Emails* url
• Wedding of Sultan url

Flood Fill/Finding Connected Components

• Il Gioco dell'X url
• The Seasonal War url
• Graph Connectivity url
• Wetlands of Florida url
• Oil Deposits url
• The die is cast url
• Lakes url
• The Same Game url
• Monkeys in a Regular Forest url
• Contour Painting url
• Maze Exploration url
• Grid Colouring url
• Deciding victory in Go url
• Counting Cells in a Blob url
• Ancient Messages* url
• Rank the Languages url
• 2D-Nim url
• You want what filled? url
• Continents* url
• Equidivisions url
• Counting Stars url
• Square Sums url
• Dominos 2 url
• Getting Gold url
• Poor Trade Advisor url
• Battleships* url

Topological Sort

• Following Orders url
• Rare Order url
• Ordering* url
• Ordering Tasks* url
• Beverages* url
• Pick up sticks url

Bipartite Graph Check

• Bicoloring* url
• Montesco vs Capuleto url
• Place the Guards* url
• Claw Decomposition* url

Finding Articulation Points/Bridges

• Network* url
• Street Directions url
• Critical Links* url
• Tourist Guide url
• Doves and bombs* url

Finding Strongly Connected Components

• Calling Circles* url
• Sub-dictionary url
• Test url
• Dominos* url
• Trust groups url
• Lighting Away url
• Come and Go* url

Minimum Spanning Tree

Standard

• Re-connecting Computer Sites url
• IP-TV url
• Oreon url
• Anti Brute Force Lock url
• Freckles url
• Transportation system.* url
• Dark roads* url
• Expensive subway url
• Airports url
• Heavy Cycle Edges* url
• Driving Range url

Variants

• Frogger url
• Heavy Cargo url
• X-Plosives url
• The Bug Sensor Problem url
• RACING url
• Audiophobia* url
• The Tourist Guide url
• Highways url
• Arctic Network* url
• Connect the Campus url
• Is There A Second Way Left? url
• ACM Contest and Blackout* url
• Traffic Flow url

Single-Source Shortest Paths (SSSP)

On Unweighted Graph: BFS, Easier

• A Node Too Far url
• Shipping Routes url
• Galactic Import url
• Word Transformation* url
• The Net url
• We Ship Cheap url
• Spreading The News* url
• The mysterious X network url
• All Roads Lead Where? url
• Knights in FEN url
• Gopher and Hawks url
• Bombs! NO they are Mines!!* url
• The Party, Part I url

On Unweighted Graph: BFS, Harder

• Robot* url
• Dungeon Master url
• Chinese Checkers url
• Getaway url
• Erdos Numbers url
• Playing with Wheels url
• Doublets url
• Enchanted Forest url
• Basic wall maze url
• Mall Mania* url
• Crazy King url
• Fire! url
• Krochanska is Here! url
• Unlock the Lock* url

On Weighted Graph: Dijkstra's, Easier

• Number Maze* url
• Mice and Maze* url
• Subway url
• Sending email* url

On Weighted Graph: Dijkstra's, Harder

• Finding Nemo url
• Travel url
• From Dusk Till Dawn url
• Fire Station url
• Rough Roads url
• Fill url
• Lift Hopping* url
• The Great Escape url
• Minefield url
• Full Tank? url
• Airport Setup url
• Babel* url
• Route Change url
• Highest Paid Toll* url
• Almost Shortest Path url

On Graph with Negative Weight Cycle: Bellman Ford's

• Wormholes* url
• Traffic* url
• XYZZY* url
• Flying to Fredericton url

All-Pairs Shortest Paths

Standard

• Non-Stop Travel url
• MPI Maelstrom url
• Risk url
• Page Hopping* url
• USHER url
• Interstar Transport url
• Meeting Prof. Miguel...* url
• Avoiding Your Boss url
• New to Bangladesh? url
• Road Construction url
• The Orc Attack url
• Thunder Mountain url
• Bear with me, again.. url
• 05-2 Rendezvous url
• Commandos* url
• Edgetown's Traffic Jams url

Variants

• Arbitrage* url
• Numbering Paths url
• Trip Routing url
• Cat and Mouse url
• Arbitrage (II) url
• Identifying Concurrent Events* url
• Airline Comparison url
• No more prerequisites, please! url
• Degrees of Separation* url
• The Geodetic Set Problem url
• The Scrooge Co Problem url

Network Flow

Standard Max Flow Problem (Edmonds Karp's)

• Software Allocation* url
• Internet Bandwidth* url
• The Problem with the Problem Setter url
• Councilling url
• Collectors Problem url
• My T-shirt suits me url
• Monkeys in the Emei Mountain* url
• Clever Naming Patterns url

Variants

• Power Transmission url
• Sabotage url
• Down Went The Titanic* url
• Angry Programmer* url
• March of the Penguins* url

Special Graphs (Others)

Tree

• Tree Summing url
• Climbing Trees url
• Trees on the level url
• Tree Recovery url
• Tree url
• Is It A Tree? url
• The Falling Leaves url
• S-Trees url
• Not so Mobile url
• Roads in the North url
• The Tree Root* url
• Pre, in and post url
• Cockroach Escape Networks* url
• Close Relatives url
• Expressions url
• Family Tree url
• Flight Planning* url
• Another Crisis url
• Binary Search Tree url

Eulerian Graph

• The Postal Worker Rings Once url
• The House Of Santa Claus url
• The Necklace* url
• Play on Words url
• Snow Clearing* url
• Morning Walk* url

Bipartite Graph

• Sorting Slides url
• The dog task url
• A Plug for UNIX url
• Machine Schedule url
• Gopher II url
• Antenna Placement* url
• Nuts and Bolts* url
• Factors and Multiples* url
• SAM I AM url
• Guardian of Decency url
• Cat vs. Dog url

Special Graph (Directed Acyclic Graph)

Single-Source Shortest/Longest Paths on DAG

• Stacking Boxes url
• Project Scheduling* url
• Longest Paths url
• Tower of Cubes url
• Hippity Hopscotch url
• Longest Run on a Snowboard* url
• Liftless EME* url

Counting Paths in DAG

• Walking on the Safe Side url
• Walking Around Wisely url
• How Many? url
• Many Paths, One Destination* url
• Injured Queen Problem* url
• How Many Dependencies? url
• Little Red Riding Hood url
• Waterland url
• Checkers* url

Converting General Graph to DAG

• Always on the run url
• Winterim Backpacking Trip* url
• TV game url
• Adventures in Moving - Part IV url
• Traveling Politician url
• Teobaldo's Trip url
• Travelling Salesman url
• Segments url
• Walking on a Grid* url
• Alternative Arborescence url
• Gathering Food* url
• Avoiding Jungle in the Dark url
• Optimal Cut url

Mathematics

Ad Hoc Mathematics Problems

The Simpler Ones

• Hashmat the Brave Warrior url
• Back to High School Physics url
• Average Speed url
• To Carry or not to Carry url
• Back to Intermediate Math* url
• Etruscan Warriors Never Play Chess url
• Numbering Roads* url
• Bafana Bafana url
• Brick Game* url
• Feynman url
• Three Families url

Mathematical Simulation (Brute Force), easier

• The 3n + 1 problem url
• Ackermann Functions url
• Perfection* url
• Continued Fractions url
• Rational Neighbor url
• Digit Counting* url
• Primary Arithmetic url
• Peter's Smokes* url
• Above Average url
• Odd Sum url
• Code Refactoring url
• Cola url
• Income Tax url
• Gourmet Games url
• Soda Surpler url
• The Coco-Cola Store url
• Magic Formula url
• Counting Game url
• Different Digits url

Mathematical Simulation (Brute Force), harder

• Rational Spiral url
• Multiplying by Rotation url
• Coconuts, Revisited* url
• Jack and Jill url
• Steps url
• The ? 1 ? 2 ? ... ? n = k problem url
• Dick and Jane url
• Super Number url
• Billiard bounces* url
• Consecutive Integers* url
• In The Airport url

Finding Pattern or Formula, easier

• Simple calculations url
• The Hotel with Infinite Rooms url
• The Land of Justice url
• f91 url
• Chessboard* url
• Throwing cards away II* url
• The least possible effort url
• Bubble Sort* url
• Very Big Perfect Squares url

Finding Pattern or Formula, harder

• Deck url
• Joana and the Odd Numbers url
• Ant on a Chessboard* url
• Cats, with or without Hats url
• R U Kidding Mr. Feynman? url
• The Eurocup is Here! url
• Traffic Volume url
• Chinese Shuffle url
• Koerner's Pub url
• Big Chocolate url
• Simple Addition url
• Black and white painting* url
• K-Multiple Free set url
• Counting Solutions to an Integral Equation url
• Dissecting a Hexagon url
• The 3-Regular Graph url
• Tri-Isomorphism url
• Fantasy of a Summation* url

Grid

• Count on Cantor* url
• Bee Breeding url
• Cantor Fractions url
• Bee Maja* url
• Dermuba Triangle* url
• A Flea on a Chessboard url
• Can You Solve It? url
• Strange Planet url

Number Systems or Sequences

• Ugly Numbers url
• Street Numbers url
• Up and Down Sequences url
• Humble Numbers* url
• Self Numbers url
• The Collatz Sequence url
• Taxicab Numbers url
• Kaprekar Numbers url
• Carmichael Numbers url
• Smith Numbers* url
• Self-describing Sequence url
• Bangla Numbers url
• Farey sequences* url
• A-Sequence url
• Sum of Product url
• B2-Sequence url
• Square Numbers url
• Look-and-Say sequences url
• Lucky Numbers url

Logarithm, Exponentiation, Power

• The Cat in the Hat url
• Power of Cryptography url
• Heads / Tails Probability url
• Heads url
• The Archeologists' Dilemma* url
• Big Number url
• Factstone Benchmark* url
• Help is needed for Dexter url
• Best Compression Ever url
• Hello World! url
• Logarithms url
• Blind Sorting url
• Cut the Silver Bar* url
• Save from Radiation url
• Excessive Space Remover url

Polynomial

• The Errant Physicist url
• Polynomial Showdown url
• Polly the Polynomial* url
• The Largest/Smallest Box ... url
• 498-bis* url
• Summation of Polynomials url
• The Polynomial Equation url
• Polynomial Remains* url
• Quotient Polynomial url
• Rain Fall url

Base Number Variants

• Cowculations* url
• Skew Binary* url
• Squares (III) url
• An Easy Problem! url
• Base Equality url
• Parity* url
• Cheapest Base url
• Base -2 url
• The Base-1 Number System url
• Nice Licence Plates url

Just Ad Hoc

• Egyptian Multiplication url
• Simply Subsets url
• Numbers That Count url
• The Trip* url
• Divide, But Not Quite Conquer! url
• Homogeneous squares url
• Humidex url
• H(n)* url
• Car url
• HST url
• Stable Grid* url

Java BigInteger Class

Basic Features

• Integer Inquiry url
• Overflow url
• Numerically Speaking url
• Adding Reversed Numbers* url
• Exponentiation url
• Numerical surprises url
• Super long sums url
• Division url
• Product url
• Counting url
• Dear GOD url
• Automorphic Numbers url
• If We Were a Child Again url
• !! Really Strange !! url
• Very Easy !!!* url
• Three powers url
• Krakovia url
• The Ghost of Programmers url
• Who said crisis? url
• Langton's Ant url
• Contract Revision url
• Multiple of 17* url
• Stopping Doom's Day url
• Bees' ancestors url

Bonus Features: Base Number Conversion

• Palindroms <---> smordnilaP url
• What Base Is This?* url
• The Bases Are Loaded url
• Basically Speaking* url
• Kibbles "n" Bits "n" Bits "n" Bits url
• Simple Base Conversion url
• Basic Remains* url
• Ternary url
• Arithmetic url

Bonus Features: Primality Testing

• Gaussian Primes url
• Sum of Consecutive Prime Numbers* url
• Simply Emirp* url
• Prime Words url
• Pseudoprime Numbers* url
• Prime Substring url

Bonus Features: Others

• MODEX* url
• Square root url
• All You Need Is Love url
• Big Big Real Numbers url
• Simplifying Fractions* url
• High-Precision Number* url

Combinatorics

Fibonacci Numbers

• Fibonacci Freeze url
• Critical Mass url
• Fibinary Numbers* url
• Brick Wall Patterns url
• Fibonaccimal Base url
• Nowhere Money url
• How Many Fibs? url
• Ray Through Glasses* url
• World Cup Noise url
• Sweet Child Makes Trouble url
• Fibonacci Numbers url
• Yet another Number Sequence* url
• Connect the Cable Wires url
• Bee url
• Fi-binary Number url
• Help My Brother (II) url
• Miles 2 Km url

Binomial Coefficients

• Extrapolation Using a Difference Table url
• Combinations url
• Pascal's Triangle of Death url
• Binomial Showdown url
• Multinomial Coefficients url
• Polynomial Coefficients url
• Find the ways !* url
• Choose and divide url
• Combination! Once Again url
• Stripe* url
• Binomial Theorem* url

Catalan Numbers

• Safe Salutations* url
• Count the Trees* url
• How many nodes ? url
• How Many Trees? url
• Expression Bracketing* url
• Facing Problem With Trees url

Others, Easier

• Uncle Jack url
• Delivery Debacle* url
• Triangle Counting* url
• Jimmy's Balls url
• Spanning Subtree* url
• Teams url
• Little Nephew url

Other, Harder

• Tile Code url
• Pizza Cutting url
• Tiling url
• The Colored Cubes url
• Diagonal* url
• How Many Points of Intersection? url
• Tri Tiling url
• A Graph Problem* url
• Musical instruments url
• Tiling Dominoes url
• Chess Queen* url
• Hapless Hedonism url
• Ordering T-shirts url

Number Theory

Prime Numbers

• Prime Cuts url
• Goldbach's Conjecture* url
• Goldbach's Conjecture (II) url
• Anagrammatic Primes url
• Jumping Champion url
• Prime Distance* url
• Summation of Four Primes url
• Goldbach and Euler url
• Twin Primes* url
• Mr. Azad and his Son!!!!! url
• Determinate Prime url
• Less Prime url
• The primary problem url
• The Super Powers url

GCD and/or LCM

• Fermat vs. Pythagoras url
• Rational Numbers from Repeating Fractions url
• Uniform Generator url
• Pi url
• Simple division* url
• LCM Cardinality* url
• GCD LCM url
• GCD url
• Doom's Day url
• Maximum GCD* url
• Harmonic Mean url

Factorial

• Factorial Frequencies* url
• Just the Facts url
• 500!* url
• I Love Big Numbers ! url
• Factorial! You Must be Kidding!!! url
• Mischievous Children* url

Finding Prime Factors

• Prime Land* url
• Prime Factors* url
• Factoring Large Numbers url
• Largest Prime Divisor* url

Working with Prime Factors

• Factors and Factorials url
• Product of digits url
• How many zero's and how many digits ? url
• Factovisors* url
• Divisibility of Factors url
• Persistent Numbers url
• Perfect P-th Powers url
• LCM* url
• Again Prime? No Time. url
• Minimum Sum LCM url
• Multifactorials url
• Sigma Function url
• Benefit* url

Functions involving Prime Factors

• Divisors* url
• Factorial Factors url
• Find Terrorists url
• Irreducable Basic Fractions* url
• Relatives url
• Send a Table url
• How Many Solutions? url
• Number Theory url
• Composite Prime url
• Reaching the fix-point. url
• A Different Kind of Sorting url
• Alternate Task* url
• Find Solutions url

Modified Sieve

• Count the factors* url
• Riemann vs Mertens* url
• Another New Function* url
• Enumerating Rational Numbers url
• Divisors url

Modulo Arithmetic

• Software CRC url
• Big Mod* url
• Ones url
• Couple-Bachelor-Spinster Numbers. url
• Ocean Deep! - Make it shallow!!* url
• The Last Non-zero Digit.* url
• Boxes of Chocolates url
• Leading and Trailing url

Extended Euclid

• Marbles* url
• Euclid Problem* url
• Rare Easy Problem url
• Play with Floor and Ceil* url

Other Number Theory Problems

• DDF url
• Biorhythms url
• Light, more light* url
• 2 the 9s url
• You can say 11 url
• Complex, difficult and complicated url
• The Huge One* url
• Number Theory for Newbies* url

Probability Theory

Standard

• France '98 url
• What is the Probability ? url
• Let's Dance !!! url
• Throw the Dice url
• Coin Toss url
• Cows and Cars* url
• Dice Throwing* url
• God! Save me url
• Tribles url
• Winning Streak* url
• Probability|Given url
• Probability url
• Vampires url
• Another lottery url
• Hats url
• Bachelor Arithmetic url
• Tennis contest url
• Airplane url

Cycle-Finding

Standard

• Repeating Decimals url
• Expanding Fractions url
• Pseudo-Random Numbers* url
• Happy Numbers url
• Last Digit url
• Powers Et Al. url
• Happy Number url
• Eventually Periodic Sequence url
• Flavius Josephus Reloaded* url
• Calculator Conundrum url
• Generate random numbers* url
• Professor Lazy, Ph.D. url

Game Theory

Standard

• A Multiplication Game url
• Find the Winning Move* url
• Stone Game url
• Euclid's Game url
• Bachet's Game url
• The Game of 31 url
• Exclusively Edible* url
• Integer Game* url
• Box Game url
• Stones url

String Processing

Ad Hoc String Processing Problems - Part 1

Cipher/Encode/Encrypt/Decode/Decrypt, Easier

• Uncompress url
• Cipher url
• Encoder and Decoder url
• The Decoder url
• Word Scramble url
• Pig-Latin url
• Do the Untwist url
• Soundex Indexing url
• Sandorf's Cipher url
• Substitution Cypher url
• Funny Encryption Method url
• Decode the Mad man url
• 2D Hieroglyphs decoder* url
• Decode the tape* url
• Known Plaintext Attack url
• Find the Telephone url
• Decoding the message. url
• One-Handed Typist* url
• Decoding url
• Digital Fortress url
• Numeral Hieroglyphs url
• Code Number url

Cipher/Encode/Encrypt/Decode/Decrypt, Harder

• Message Decoding url
• Key to Success url
• Caesar Cypher* url
• Compression (II) url
• Decode url
• Baudot Data Communication Code url
• Burrows Wheeler Decoder url
• Crypt Kicker II url
• The Vigenère Cipher url
• Da Vinci Code* url
• Playfair Cipher* url

Frequency Counting

• What's The Frequency, Kenneth? url
• Word Problem url
• Password Search* url
• What's Cryptanalysis? url
• Tell me the frequencies! url
• Common Permutation* url
• Word Length and Frequency url
• Election url
• List of Conquests url
• GNU = GNU'sNotUnix url
• Prime Frequency url
• Can you decide it for ME?* url
• Letter Frequency url

Input Parsing (Non Recursive)

• Simply Syntax url
• Evaluating Simple C Expressions url
• Mark-up url
• Equation Elation url
• Matrix Chain Multiplication url
• English-Number Translator url
• Artificial Intelligence? url
• A DP Problem url
• Strange Integration* url
• Moliu Fractions url
• Ensuring Truth* url
• Homework Checker* url
• Longest Word url

Input Parsing (Recursive)

• Slurpys url
• Sentence/Phrase Generator url
• Cellular Structure url
• Grammar Evaluation* url
• The MTM Machine url
• Number of Paths* url
• The Good Old Times url
• Smeech* url

Solvable with Java String/Pattern class (Regular Expression)

• Identifying Legal Pascal Real Constants* url
• Kindergarten Counting Game* url
• Haiku Review url
• Jimmi's Riddles* url

Ad Hoc String Processing Problems - Part 2

Output Formatting

• Meta-Loopless Sorts url
• Word Crosses url
• Border url
• Inventory Maintenance url
• Long Multiplication url
• Romulan Spelling url
• Fifth Bank of Swamp County url
• Marvelous Mazes url
• Triangle Wave* url
• Rotating Sentences url
• Stats url
• File Mapping url
• Maze (II) url
• Team Arrangement url
• The Tower of ASCII url
• Robot maps url
• Broken Keyboard url
• Not That Kind of Graph* url
• Big Math url
• Save Hridoy url
• Draw Grid url
• Building a Triangular Museum url
• Extra Spaces url
• ASCII Diamondi* url
• In Braille url

String Comparison

• Excuses, Excuses! url
• Immediate Decodability* url
• Spell checker url
• Live From Mars url
• Automatic Correction of Misspellings* url
• Formula 1* url
• Deli Deli url
• Abstract Names url
• Big Number of Teams will Solve This url

Just Ad Hoc

• Permalex url
• Number Chains url
• Finding words url
• Permutations* url
• String Cutting url
• Greatest K-Palindrome Substring url
• Automatic Editing url
• Zipf's Law url
• Learning Portuguese url
• Automatic Poetry url
• Compound Words url
• The One-Handed Typist* url
• Word Morphing url
• I Love Strings!! url
• Dancing the Cheeky-Cheeky* url
• Code Creator url
• Optical Reader url
• DNA II url
• Flowers Flourish from France url
• Calculating Yuan Fen url

String Matching

Standard

• Periodic Strings url
• Named Extension Dialing url
• Power Strings* url
• Phone List url
• Extend to Palindrome* url
• Scrolling Sign* url
• Abnormal 89's url
• Secret Word url

In 2D Grid

• Word-Search Wonder* url
• The Boggle Game url
• Lost in Space url
• Where's Waldorf?* url
• Playing Boggle* url

String Processing with Dynamic Programming

Classic

• String Computer url
• String Distance and Transform Process* url
• Compromise url
• AGTC url
• The Twin Towers url
• Longest Match url
• Vacation* url
• Longest Common Subsequence url
• Prince and Princess* url
• String to Palindrome url

Non Classic

• Palinwords url
• Make Palindrome url
• Again Palindrome url
• String Factoring* url
• Longest Palindrome* url
• String Partition* url
• Fewest Flops url

Suffix Trie, Tree, Array

Standard

• Glass Beads url
• DNA Sequencing* url
• Editor url
• Top 10 url
• Life Forms* url
• GATTACA* url

(Computational) Geometry

Basic Geometry - Part 1

Points and Lines

• Tree's a Crowd url
• Intersection url
• Intersecting Lines url
• There's treasure everywhere! url
• Water Falls url
• Light and Transparencies url
• Sunny Mountains* url
• Euclid url
• Fourth Point !! url
• The Other Two Trees url
• Railway* url
• Playball !!! url
• How Far? url
• Center of symmetry url
• Yoyodyne url
• Brownie Points url
• Pick-up Sticks url
• Bright Lights* url
• An Easy Task url
• Isolated Segments url
• Logo url
• Logo 2 url
• Genius MJ url

Triangles (plus Circles)

• Pipe Fitters url
• Orchard Trees url
• Circle Through Three Points url
• Inscribed Circles and Isosceles Triangles url
• The Circumference of the Circle url
• The Knights Of The Round Table url
• Romeo and Juliet ! url
• Trouble with a Pentagon url
• Medians url
• Billiard url
• Height to Area url
• Bounding box* url
• The Laurel-Hardy Story url
• Region url
• Colourful Flowers* url
• Kingdom Division url
• Triangular Pegs in Round Holes url
• Laser Pointer url
• Triangle Fun url
• Is this the easiest problem? url
• Triangle Trouble url
• Egypt url
• Soya Milk* url
• The Lazy Lumberjacks url

Basic Geometry - Part 2

Circles (only)

• Graveyard url
• Packing polygons* url
• Chocolate Chip Cookies url
• Rope Crisis in Ropeland! url
• Is This Integration ? url
• Satellites url
• The Kissing Circles url
• Polygon Inside A Circle url
• Ancient Village Sports url
• Geometry Paradox url
• Area* url
• The Grazing Cow* url
• 10:6:2 url

Quadrilaterals

• All Squares url
• Overlapping Rectangles* url
• Points in Figures: Rectangles url
• Points in Figures: Rectangles and Circles url
• The easiest way* url
• Rectangles url
• Behold my quadrangle url
• Guard the Land url
• Determine the Shape url
• Elevator* url
• Making Quadrilaterals url

3D Objects

• Gleaming the Cubes* url
• Flooded!* url
• Beavergnaw* url

Polygon

Standard

• SCUD Busters url
• Polygons url
• Moth Eradication url
• Cops and Robbers url
• Points in Figures: Rectangles, Circles, Triangles url
• The Incredible Hull url
• Polygon url
• Convex Hull Finding url
• Berry Picking url
• Trash Removal* url
• Boundary Points url
• Center of Masses url
• A hole to catch a man url
• Useless Tile Packers url
• Myacm Triangles url
• Cutting tabletops url
• Board Wrapping* url
• Nails url
• The Sultan's Problem* url
• Reservoir logs url
• Campus Roads url
• Convex Hull url

More Advanced Topics

More Advanced Search Techniques

More Challenging Backtracking Problems

• The Psychic Poker Player url
• The Game url
• Dividing up url
• Su Doku url
• Bit Compressor url
• Turn the Lights Off* url
• Security Panel url
• Maze url
• So Doku Checker url
• Another n-Queen Problem* url
• A Gentlemen's Agreement* url
• Triple-Free Binary Strings url
• Even Parity url
• Arrange the Tiles url

More Challenging State-Space Search with BFS or Dijkstra's

• The New Villa url
• It's not a Bug, it's a Feature! url
• Eternal Truths url
• Round and Round Maze* url
• Routing url
• Repeated Substitution with Sed url
• Infected Land url
• The Monocycle url
• The Color Game url
• Seven Seas url
• Dancing Digits* url
• Curious Fleas* url
• 9 Puzzle url
• Switch The Lights url
• Switch Bulbs url

Meet in the Middle/A*/IDA*

• Eight url
• Robots on Ice* url
• Route Planning url
• 15-Puzzle Problem* url
• Jaguar King url
• Editing a Book* url

Problem Decomposition

Two Components - Binary Search the Answer and Other

• Copying Books url
• Against Mammoths url
• Curvy Little Bottles url
• Leaps Tall Buildings (in a single bound) url
• Crossed Ladders url
• Opening Doors url
• Expanding Rods url
• Gopher Strategy url
• Travel in Desert url
• Buy one, get the rest free* url
• Weird Fence* url
• WiFi* url
• Athletics Track url
• Enemy at the Gates url

Two Components - Involving DP 1D RSQ/RMQ

• Circular url
• Prime Time url
• Digit Primes url
• Primed Subsequence url
• Game of Sum* url
• Semi-prime H-numbers* url
• Count DePrimes* url
• Erasing and Winning url
• A Gift from the Setter url

Two Components - Graph Preprocessing and DP

• Bridge Building* url
• Walk Through the Forest url
• Blackbeard the Pirate url
• Nuts for nuts.. url
• The Largest Clique* url
• Can U Win?* url
• Speedy Escape url
• Shopping url

Two Components - Involving Graph

• Jack Straws url
• Gossiping url
• Simplified GSM Network url
• Tracking Bio-bots* url
• Polynomial-time Reductions url
• Mines url
• Airlines url
• Killing Aliens in Borg Maze url
• The Hire-a-Coder Business Model url
• Hotel booking* url
• Instant View of Big Bang url
• Number Transformation url
• Invite Your Friends url
• Prime Path url
• Gun Fight* url

Two Components - Involving Mathematics

• Calling Extraterrestrial Intelligence Again url
• The Lottery url
• Naughty Sleepy Boys url
• Almost Prime Numbers* url
• Coprimes* url
• Mint* url
• Mixing Invitations url
• Count the Factorials url
• Cubes url

Two Components - Complete Search and Geometry

• Mouse Clicks url
• Laser Lines url
• Squares url
• Lining Up url
• Square Pegs And Round Holes url
• Finding Rectangles url
• Mobile Phone Coverage url
• How Big Is It?* url
• Birthday Cake url
• Rings and Glue url
• Dog and Gopher url
• Of Circles and Squares url
• The silver bullet.* url
• Cranes url
• Colliding Traffic* url

Two Components - Mixed with Efficient Data Structure

• Crypt Kicker url
• Rectangle by the Ocean url
• Triangle Partitioning url
• Dying Tree* url
• Permutation* url
• Divisor Game* url
• Galactic Bonding url
• Hic-Hac-Hoe url
• Digital Roulette url
• Careful teacher url

Three Components

• Fatman* url
• The Fortified Forest url
• The Traveling Judges Problem* url
• A Careful Approach url
• Castles url
• Robot Challenge url
• Recover Factorial url
• Factory Robot url
• Reverse Prime* url

More Advanced DP Techniques

DP level 2

• The Bridges of Kolsberg* url
• Atomic Car Race* url
• Distinct Subsequences url
• Tight Words url
• Square url
• Sum-up the Primes url
• Game of Euler url
• Pebble Solitaire url
• Expression Again url
• Combo Deal url
• Forming Quiz Teams* url
• End up with More Teams url
• Account Book url
• KTV url
• Philip J. Fry Problem url

DP level 3

• Scheduling Lectures url
• The Vindictive Coach url
• Trade on Verweggistan url
• The Mailbox Manufacturers Problem url
• ACORN* url
• Free Parentheses* url
• ICPC Team Strategy url
• Palindromic paths url
• Edit Step Ladders url
• Tug of War url
• Weights and Measures url
• Storage Keepers url
• Number Game url
• Chopsticks url
• Optimal Binary Search Tree url
• Chemical Reaction url
• Menu url
• Headmaster's Headache url
• Towards Zero url
• Anagram Division url
• Exchange Rates url
• Blobs in the Board* url
• Help the Winners url

DP level 4

• Raucous Rockers url
• Sharing Chocolate* url
• Party at Hali-Bula* url
• Bribing FIPA url
• Twenty Questions* url
• Yahtzee url
• The Candyman Can url
• Buying Coke url
• Super Lucky Numbers url
• Arrange Some Marbles url
• Eigensequence url
• Busy Programmer url
• Beautiful Numbers url

Rare Topics

Rare Algorithms

Dinic's Algorithm

• Monkeys in the Emei Mountain* url

Formulas or Theorems

• Trees on My Island url
• Count the Faces. url
• How Many Pieces of Land ?* url
• Graph Construction* url
• Anne's game url
• Dream url
• Gridland Airports* url

Gaussian Elimination

• Stupid Sequence* url

Great-Circle Distance

• Globetrotter* url
• Airline Hub* url
• Travelling Distance url
• Tunnelling the Earth* url

Hopcroft Karp's Algorithm

• Nuts and Bolts* url

Kosaraju's Algorithm

• Come and Go* url

Matrix Power

• Modular Fibonacci url
• How Many Calls?* url
• Contemplation! Algebra* url
• Recurrences url
• Finding Paths in Grid* url
• Tribonacci url

Pollard's rho Integer Factoring Algorithm

• Factorizing Larget Integers* url

Sliding Window

• Subsequence* url
• Smallest Sub-Array* url

Rare Problems

2-SAT Problem

• Manhattan* url

Art Gallery Problem

• Video Surveillance* url
• The Art Gallery* url
• Fire! Fire!! Fire!!!* url

Bitonic TSP

• The Islands* url
• Tour* url

Bracket Matching

• Nesting a Bunch of Brackets* url
• Parentheses Balance* url
• Generalized Matrioshkas* url

Chinese Postman Problem

• Jogging Trails* url

Closest Pair Problem

• The Closest Pair Problem* url
• Bey Battle* url

Graph Matching (non-bipartite)

• Maximizing the ICPC* url

Independent and Edge Disjoint Paths

• Crimewave* url
• Necklace* url

Inversion Index

• Train Swapping url
• DNA Sorting* url
• Flip Sort* url
• Ultra-QuickSort url
• Bubbles and Buckets url
• Frosh Week* url

Josephus Problem

• Roman Roulette url
• The Dole Queue url
• Power Crisis url
• Joseph url
• MAS*H url
• Eeny Meeny Moo url
• Joseph's Cousin url
• Barbarian tribes* url
• Repeated Josephus* url
• Last Man Standing* url

Knight Moves

• Knight Moves* url
• Knight Tour* url

Lowest Common Ancestor

• Flea circus* url
• Ants Colony* url

Magic Square Construction (odd size)

• Magic Square* url

Matrix Chain Multiplication

• Optimal Array Multiplication Sequence* url

Min Cost (Max) Flow

• Data Flow url
• Crime Wave - The Sequel* url
• Dijkstra, Dijkstra. url
• Warehouse* url
• Great Wall of China* url

Min Path Cover on DAG

• Air Raid* url
• Taxi Cab Scheme* url

Pancake Sorting

• Stacks of Flapjacks* url

Postfix Calculator and Conversion

• Equation* url

Roman Numerals

• Roman Digititis* url
• The Return of the Roman Empire url
• Roman Numerals* url
• Roman Numerals* url

Sorting in Linear Time

• Age Sort* url

Tower of Hanoi

• The Never Ending Towers of Hanoi* url