Problem Collection

We have many ways for you to practice for upcoming competitions:

To search problems or browse by venues, languages, etc., check out the NACLO problem database

NACLO 2022 Problems

Name Solution Author
Lines in the Sand Solution Michael Salter
Who Saw the Bear? Solution Tom McCoy
To Make a Long Story Short Solution Ryan Chi
Real Numbers Solution Daniel Lovsted
Sleeping in the Shade Solution Aleka Blackwell
Splash to Save Solution Catherine Scanlon
Out of Order Solution Tom McCoy
From Soup to Nuts Solution Simi Hellsten
A Cornish Conundrum Solution Babette Verhoeven
Sounds Fishy Solution Harold Somers
A Tough Word to Swallow Solution Ryan Chi
Stopping for a Spell Solution Tom McCoy
A Splitting Disagreement Solution Gordon Chi
Pseudorandom Numbers Solution Simi Hellsten
Seeing the Future Solution Andrés Pablo Salanova
Yumology Solution Ali Sharman
Relatively Speaking Solution Simi Hellsten
I Stop Being Afraid of This Problem Solution Ethan Chi and David Mortensen
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2021 Problems

Name Solution Author
The Tortoise and the Rabbit Solution Tom McCoy
Junk Mail: Letters We Don't Need Solution Tom McCoy
Versatile Verb Solution Aleka Blackwell
Made You Look! Solution Tom McCoy
The Script of Your Dreams Solution Ryan Chi
The Wiles of Reptiles Solution Daniel Lovsted
The Skates of Wrath Solution Ryan Chi
Sequitur Solution Pranav Krishna and Daniel Lovsted
Non Sequitur Solution Daniel Lovsted
A Vintage Sound System Solution Ethan Chi
Putting a Place to a Name Solution Harold Somers
Is This Problem Intelligible? Solution Evan Hochstein
The Speech Has No End Solution Simi Hellsten
Do I Care about Duikers? Solution Ethan Chi
Cameroonian Compounds Solution Aleka Blackwell
Family Ties Solution Gordon Chi
A Stress Test Solution Tom McCoy and Ryan Chi
GloVe Compartment Solution Pranav Krishna
Peace Only Solution Ethan Chi and Daniel Lovsted
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2020 Problems

Name Solution Author
Let That Mongo! Solution Kevin Liang
A Cat in a Hat Solution Aleka Blackwell
Set in Stone Solution Ethan Chi
Pay Attention Solution Ethan Chi
Breton Numbers Solution Michael Salter
Coming into Focus Solution Sam Ahmed
Password Confusion Solution Tom McCoy
The Idalion Tablet Solution Michael Salter
Kãa, Kai, and Khai Solution Ethan Chi
You Made Me See Solution Sam Ahmed
The Pimpled Toad Solution Ethan Chi
Shiva Sutras Solution Ben LaFond
Adjupectiheaval! Solution Ethan Chi
You Can’t Handle the Truth Solution Daniel Lovsted
We’re Counting on Yoruba Solution Harold Somers
Doubling Up on Nakanai Solution Ethan Chi
Cut to the Chase Solution Lori Levin and Tom McCoy
The Obviative Solution Solution Daniel Lovsted
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2019 Problems

Name Solution Author
Malteaser Solution Harold Somers
You Speak Ndebele, Don't You? Solution Michael Salter
Here is One Hand Solution Daniel Lovsted
Predicate Etiquette Solution Daniel Lovsted
Hate It or Lopit Solution Jonathan Moodie and Rosey Bilington
Harmongolia Solution Ethan Chi
Break it Down! Solution Tom McCoy and Sonia Reilly
Can you know/Hanunó'o Solution Ethan Chi
The Afrihili Word Machine Solution Michael Salter and Aleka Blackwell
Polish These Nouns! Solution Milena Veneva
Two Róngs Don't Make a Right Solution Ethan Chi
We Were Born to Solve This Problem Solution Daniel Lovsted
Colorless Green Concepts Scripting Furiously Solution Daniel Lovsted
Fun With Witsuwit'en Solution Daniel Lovsted
Infer a Surprise Solution Tom McCoy
Do You Hear the Master's Moon Solution Sam Ahmed
A Tale of Kieu-plets Solution Ethan Chi
Disambiguate This! Solution Ethan Chi
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2018 Problems

Name Solution Author
At Ease in Gilbertese Solution Michael Salter
The Pame Game Solution Milena Veneva
All Roads Lead to Tirana Solution Ali Sharman
Intergalactic Grammars Solution Ali Sharman
Parties in Palauan Solution Michael Salter
A Match Made in Vietnam Solution Tom McCoy
By the Same Token Solution Tom McCoy
N'ko, M'kay Solution Babette Newsome and Harold Somers
A Menya Puzzle Solution Aleka Blackwell
It's True: The Truth About Chalcatongo Mixtec Solution Babette Newsome
Sri Lankan Names Solution Ali Sharman and Tom McCoy
Peeled Potato Act with Annie Solution Ali Sharman
Quests and Requests in Nivkh Solution Heather Newell
You've Got This: Fijian Ownership Solution Vica Papp
To Know or Not to Know Literary Tamil Solution Babette Newsome
I Know What I Saw Solution Harold Somers and Dick Hudson
Better Left Unsaid Solution Tom McCoy
A Make-Shift Code Solution Tom McCoy
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2017 Problems

Name Solution Author
A Little Tshiluba Solution Tom McCoy
Pho Bar Solution James Hyett
LOLWUT Solution Jordan Ho, Patrick Littell, and Tom McCoy
Let's Roll! Solution Deryle Lonsdale
On the Right Track Solution Kai Low Rui Hao
Transition(al) Numbers Solution Harold Somers
Magik Yup’ik Solution Kai Low Rui Hao
Nothing but (Net)works Solution Tom McCoy
Basque Tasque Solution Aleka Blackwell
The Norwegian Problem / A Norwegian Problem / Norwegian Problems / The Norwegian Problems? Solution Babette Newsome
Sentences that go on and on and on and on Solution Jonathan Kummerfeld
The Goat, the Mother, and the Wardrobe Solution Samuel Andersson, Oliver Sayeed, and Elysia Warner
It will be you who solves this problem! Solution Aleka Blackwell
To Be Determined Solution Kai Low Rui Hao
Common Sense Solution Jordan Ho
Do you see what I see? Solution Heather Newell
Pluses and Minuses Solution Milena Veneva
Text-o-matic Solution Daniel Lovsted
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2016 Problems

Name Solution Author
Tangled up in Nots Solution Bozhidar Bozhanov
DAWG Breeds Solution Patrick Littell
The Curious Case of Estonian Solution Praveen Venkataramana
That's an Order Solution Dorottya Demszky, Yiwei Luo, and Tom McCoy
Be There, or be Squared Solution Bill Huang
Take one Tablet and Call me in the Morning Solution Dorottya Demszky
Signs from Above Solution James Hyett
Fan Fiction Solution Ben King
Deriving Enjoyment Solution Harold Somers and Simona Klemenčič
Get Edumacated Solution Patrick Littell
Kings, Queens, and Counts Solution Tom McCoy
The Short Hand of the Law Solution Dragomir Radev and Patrick Littell
Sound Judgments Solution Ollie Sayeed
What Happened at the Chess Tournament? Solution Vica Papp
Don't Sell the House Solution Alex Wade
A matter of Horn clauses Solution Josh Falk
A cup of Javanese Solution Tae Hun Lee
Changing the Subject Solution Harold Somers
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2015 Problems

Name Solution Author
The Big Dog and the Young Man Solution Mike Swan
Delphi has the Answers Solution Bozhidar Bozhanov
Aymara Rules Solution Josh Falk
Elder Futhark Runes Solution Catherine Sheard
Use the Force Solution Jonathan May
My Friend Nomura from Osaka Solution Harold Somers
Zoink! Solution Dragomir Radev, Christiane Fellbaum, and Jonathan May
Phaasaa and Phaasaa Solution Alex Wade
Old English Solution Graeme Trousdale
Georgian Transitive Verbs Solution Dorottya Demszky and Adam Hesterberg
The Dualization Game Solution Daniel Lovsted
Easy-Peasy-Malagasy Solution Tom McCoy
Minimum Spelling Trees Solution John de Nero
Maxakali Solution Alexander Wade and Pat Littell
Do-This-Do-That Solution David Mortensen
The Old Man the Boats Solution Emily Bender
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2014 Problems

Name Solution Author
What's the Time in Tallinn? Solution Babette Newsome
Māori Loanwords Solution Patrick Littell
Levenshtein's Fine Signs Solution Blake Allen and Patrick Littell
Wheel of Fortune Cookies Solution Patrick Littell
Visible Speech Solution Natalie Weber and Patrick Littell
Lontara Solution Chelsea Voss
Cameroon Pidgin English Solution Aleka Blackwell
Bertrand and Russell Solution Ben King
To play or not to play Solution Catherine Sheard
Lexicondensed Solution Tom McCoy
Don't be Ukhrul to a Liver that's True Solution David Mortensen
Transducing Runes Solution Jordan Boyd-Graber
Come to Istanbul Solution David Palfreyman
Hungarian Rocks Solution Adam Hesterberg
CCG Solution Jonathan Kummerfeld, Aleka Blackwell, and Patrick Littell
Combining Categories in Tok Pisin Solution Jonathan Kummerfeld, Aleka Blackwell, and Patrick Littell
Learning Yidiny Solution Mary Laughren
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2013 Problems

Name Solution Author
Intuitive Inuit Solution Harold Somers
A Case of Pali Solution Babette Verhoeven
The Heads and Tails of Huffman Solution John DeNero
Kwak'wala Word Search Solution Patrick Littell
Shaw Business Solution Babette Verhoeven
Grammar Rules! Solution Andrea Schalley and Patrick Littell
Phoenician Fun Solution Harold Somers
Twodee Solution Jason Eisner
Beja Solution Richard Hudson
Stockholms Tunnelbana Solution Patrick Littell
Putting the Books in Order Solution Dragomir Radev
Yesbot Solution Patrick Littell
Playing the Cognate Game Solution Catherine Sheard
A Tree by Any Other Name Solution John DeNero
Warlpiri Kinship Groups Solution Alan Chang
Deer Father Solution Patrick Littell
Grice's Grifter Gadgets Solution Jordan Boyd-Graber
Poles Apart Solution Dragomir Radev
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2012 Problems

Name Solution Author
Cat and Mouse Story Solution Patrick Littell
Learn Yolmo with pleasure Solution Lauren Gawne
Interstellar First Contact Solution Simon Zwarts, based on work by Kevin Knight
All in the Family Solution Dragomir Radev
Traevölörs Freisbuk Solution Patrick Littell
Crocodile Bardi Solution Catherine Sheard
Haitian Creole Solution Ivaylo Youmerski
Waorani Numbers Solution Dragomir Radev
The silence of the goats Solution Alexey Pegushev
Ik heb voorspeld Solution Dick Hudson
A fox among the h Solution Pat Littell
Who is good? Solution Dick Hudson
The Deschamps Codice Solution Alexander Piperski
Waanyi Solution Mary Laughren
The Little Engine that Could...Read Solution Pat Littell and James Pustejovsky
Jeg kan tælle Solution Harold Somers
100 Surnames Solution Pat Littell
One, Two, Tree Solution Noah Smith, Kevin Gimbel, and Jason Eisner
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2011 Problems

Name Solution Author
Running on MT Solution Harold Somers
Mix Up on the Farm Solution Lori Levin
The War of the Dots Solution Patrick Littell
Double or Quit in Caterpillar Country Solution Mark Dras
BrokEnglish! Solution Patrick Littell
Tiger Tale Solution Dragomir Radev
Ulwa Possessives Solution Richard Sproat
Counting in Irish Solution Tom Payne
A Large Spoon is Enough Solution Harold Somers
Axolotl in the Water Solution John Berman
A Script for the Ndyuka Solution Patrick Littell
Swallow the Salt Solution Bozhidar Bozhanov
Word Salad Solution Eric Breck
Stopping and Flapping in Warlpiri Solution Mary Laughren
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2010 Problems

Name Solution Author
Gelda's House of Gelbelgarg Solution Patrick Littell
Say It in Abma Solution Cindy Schneider
Lost in Yerevan Solution Dragomir R. Radev
Huevos y Pimientos Solution Dragomir R. Radev
Texting, Texting, One Two Three Solution Patrick Littell
Türkış Delıt Solution Bozhidar Bozhanov
Tangkhul Tangle Solution David Mortensen
Ardhay Uzzlepay Solution John Henderson with the assistance of Sophie Crouch, University of Western Australia. Based on Crouch (2008, 2009) and data from the MPI EVA Minangkabau corpus
Dogs and cats on trees Solution Emily Bender
Plains Cree Solution Patrick Littell and Julia Workman
F u cn rd ths Solution Richard Sproat
Real Money Solution Patrick Littell
No smoke without fire Solution Aleka Blackwell
Tale of Kieu Solution David Mortensen and Patrick Littell
Possessed in Vanuatu Solution Jane Simpson, University of Sydney and Jeremy Hammond, Max Planck Institute for Psycholinguistics
Khipu Solution Patrick Littell and Erin Donnelly
All Round 1 Problems All Solutions
All Round 2 Problems

NACLO 2009 Problems

Name Solution Author
Tenji karaoke Solution Patrick Littell
Nok-nok! Solution Eugene Fink
Letters for Cuzco Solution Patrick Littell
You will be laughing Solution Bozhidar Bozhanov
Summer Eyes Solution Dragomir Radev and Adam Hesterberg
Help my camera! Solution Emily Bender
Sk8 Parsr Solution Patrick Littell
Linear Combinations Solution Richard Sproat
Easy Pieces Solution Todor Tchervenkov
Hypo-Hmong-driac Solution David Mortensen
The gerbil arrived Solution Bozhidar Bozhanov
Yak, Du, Dray Solution Dragomir Radev
Orwellspeak Solution Jason Eisner
All Round 1 Problems All Solutions
All Round 2 Problems

NACLO 2008 Problems

Name Solution Author
Of monkeys and children Solution Ronnie Sim and Thomas Payne
Springing up baby Solution Ankit Srivastava and Emily Bender
Reach for the top Solution Patrick Littell
Spare the Rod Solution Dragomir Radev
A Fish Story Solution Patrick Littell
Fakepapershelfmaker Solution Willie Costello
Manam, I'm Anam Solution Patrick Littell
Thorny Stems Solution Eric Breck
aw-TOM-uh-tuh Solution Patrick Littell
The Curragh of Kildare Solution Todor Tchervenkov
Tzolk'in Solution Patrick Littell and Erin Donnelly
The Whole Spectrum Solution Adam Hesterberg
All Round 1 Problems All Round 1 Solutions
All Round 2 Problems All Round 2 Solutions

NACLO 2007 Problems

Name Solution Author
We are all molistic in a way Solution Dragomir Radev
Pooh's encyclopedia Solution Eugene Fink
A donkey in every house Solution Todor Tchervenkov
Hmong Solution Ivan Derzhanski
Better sorry than shunk Solution Jason Eisner and Roy Tromble
The lost tram Solution Boris Iomdin
Rewrite me badd Solution Patrick Littell and David Mortensen
This problem is pretty // easy Solution Dragomir Radev
All Problems All Solutions

Student Contributed Problems

Name Solution Author
Hebrew Morris Alper
Japanese Morris Alper
Tamil Solution Anand Natarajan
Welsh Solution Anand Natarajan
Yers Solutions Anand Natarajan

NACLO Online Practice

NACLO Online Practice is an interactive online system that allows you to practice with problems from previous competitions and have them automatically scored. Below is a list of problems that are included in this system. Click on a problem's title to be taken to that problem's page.

Sample Practice Problems

Name Solution Author
Agta Solution Tom Payne
Alliteration Solution Jason Eisner and Roy Tromble
Ambiguous Solution Emily Bender
Amharic Solution Yekaterina Iassinskaya
Anishinaabemowin Solution Patrick Littell
Cognates Solution Dragomir Radev
Finite-state transducers Solution Richard Sproat
Finite-state transducers Solution Tom Payne
Handwriting recognition Solution Tom Payne
Hieroglyphics Solution Tom Payne
Luvian Solution A. Zhurinsky
Maa Solution Doris L. Payne
Magicsquare Solution John Blatz
Phonebook Solution Jason Eisner and Roy Tromble
Scrabble Solution Roy Tromble
Tamil Solution Eric Pederson
Transformations Solution Lori Levin
Walrus Solution Boris Iomdin
Weasel Solution John Blatz and Jason Eisner

Problems from Other Sources