IOI Problems and Solutions
Competitors are given algorithmic problems and write programs to solve them, scored automatically against test data rather than read by a marker. Two competition days, three tasks on each. First held at Pravetz, Bulgaria in 1989.
2025
Bolivia
Problems 6 problems
1 Souvenirs Problem IOI 2025 problem 1, Souvenirs 2 Triple Peaks Problem IOI 2025 problem 2, Triple Peaks 3 World Map Problem IOI 2025 problem 3, World Map 4 Festival Problem IOI 2025 problem 4, Festival 5 Migrations Problem IOI 2025 problem 5, Migrations 6 Obstacles for a Llama Problem IOI 2025 problem 6, Obstacles for a Llama
2024
Egypt
2023
Hungary
Problems 6 problems
1 Closing Time Problem IOI 2023 problem 1, Closing Time 2 Longest Trip Problem IOI 2023 problem 2, Longest Trip 3 Soccer Problem IOI 2023 problem 3, Soccer 4 Beech Tree Problem IOI 2023 problem 4, Beech Tree 5 Overtaking Problem IOI 2023 problem 5, Overtaking 6 Robot Contest Problem IOI 2023 problem 6, Robot Contest
2022
Indonesia
Problems 6 problems
1 Catfish Farm Problem IOI 2022 problem 1, Catfish Farm 2 Prisoner Challenge Problem IOI 2022 problem 2, Prisoner Challenge 3 Radio Towers Problem IOI 2022 problem 3, Radio Towers 4 Digital Circuit Problem IOI 2022 problem 4, Digital Circuit 5 Rarest Insects Problem IOI 2022 problem 5, Rarest Insects 6 Thousands Islands Problem IOI 2022 problem 6, Thousands Islands
2021
Singapore (remote)
Problems 6 problems
1 Candies Problem IOI 2021 problem 1, Candies 2 Keys Problem IOI 2021 problem 2, Keys 3 Parks Problem IOI 2021 problem 3, Parks 4 DNA Problem IOI 2021 problem 4, DNA 5 Dungeons Problem IOI 2021 problem 5, Dungeons 6 Registers Problem IOI 2021 problem 6, Registers
2020
Singapore (remote)
Problems 6 problems
1 Plants Problem IOI 2020 problem 1, Plants 2 Supertrees Problem IOI 2020 problem 2, Supertrees 3 Tickets Problem IOI 2020 problem 3, Tickets 4 Biscuits Problem IOI 2020 problem 4, Biscuits 5 Mushrooms Problem IOI 2020 problem 5, Mushrooms 6 Stations Problem IOI 2020 problem 6, Stations
2019
Azerbaijan
2018
Japan
2017
Iran
2016
Russia
2015
Kazakhstan
2014
Taiwan
2013
Australia
Problems 6 problems
1 Dreaming Problem IOI 2013 problem 1, Dreaming 2 Art Class Problem IOI 2013 problem 2, Art Class 3 Wombats Problem IOI 2013 problem 3, Wombats 4 Cave Problem IOI 2013 problem 4, Cave 5 Robots Problem IOI 2013 problem 5, Robots 6 Game Problem IOI 2013 problem 6, Game
2012
Italy
2011
Thailand
2010
Canada
2009
Bulgaria
2008
Egypt
2007
Croatia
2006
Mexico
2005
Poland
2004
Greece
2003
United States
Problems 6 problems
1 Trail Maintenance Problem IOI 2003 problem 1, Trail Maintenance 2 Comparing Code Problem IOI 2003 problem 2, Comparing Code 3 Reverse Problem IOI 2003 problem 3, Reverse 4 Guess Which Cow Problem IOI 2003 problem 4, Guess Which Cow 5 Amazing Robots Problem IOI 2003 problem 5, Amazing Robots 6 Seeing the Boundary Problem IOI 2003 problem 6, Seeing the Boundary
2002
South Korea
2001
Finland
2000
China
1999
Turkey
Problems 6 problems
1 Little Shop of Flowers Problem IOI 1999 problem 1, Little Shop of Flowers 2 Hidden Codes Problem IOI 1999 problem 2, Hidden Codes 3 Underground City Problem IOI 1999 problem 3, Underground City 4 Traffic Lights Problem IOI 1999 problem 4, Traffic Lights 5 Flatten Problem IOI 1999 problem 5, Flatten 6 A Strip of Land Problem IOI 1999 problem 6, A Strip of Land
1998
Portugal
1997
South Africa
1996
Hungary
1995
Netherlands
1994
Sweden
1993
Argentina
Problems 4 problems
1 Problem 1 Problem IOI 1993 problem 1 2 Problem 2 Problem IOI 1993 problem 2 3 Problem 3 Problem IOI 1993 problem 3 4 Problem 4 Problem IOI 1993 problem 4
1992
Germany
1 Mysterious Continents not published 2 A Mazing Workshop not published 3 Islands in the Sea not published 4 Hamilton's Robot not published 5 Climbing a Mountain not published 6 Rubik's Toolkit not published
1991
Greece
1 Playcard Problem not published 2 Trees Problem not published 3 Square Problem not published 4 Languages Problem not published Problems 1 problem
5 S-terms Problem Problem IOI 1991 problem 5, S-terms Problem
1990
Soviet Union
Problems 2 problems
1 Round 1 Problem IOI 1990 problem 1, Round 1 2 Round 2 Problem IOI 1990 problem 2, Round 2
1989
Bulgaria
Problems 6 problems
1 Problem 1 Problem IOI 1989 problem 1 2 Problem 2 Problem IOI 1989 problem 2 3 Problem 3 Problem IOI 1989 problem 3 4 Problem 4 Problem IOI 1989 problem 4 5 Problem 5 Problem IOI 1989 problem 5 6 Problem 6 Problem IOI 1989 problem 6
Problem PDF: Problems PDF: Solution PDF: Solutions PDF: Marking scheme PDF: Marking scheme PDF: Problems and solutions PDF: Problems and solutions PDF: LaTeX source (.zip): LaTeX source (.zip): Add to list: More materials:
