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Challenges
Dive into our coding challenges to have fun and acquire new skills. Join us in chat to discuss!
17 challenges
Sorted by:
27
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3k
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47
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Challenge #16: Change is the only constant
After more than 230 years of production, the United States made its final one-cent coin in late 2025. That news got us thinking about how to add up coins to create change. Image from IStock Here’s ...
- 4,513
76
votes
6k
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102
entries
Challenge #15: Mystery Alphabet Decoder [COMPLETED]
Update on February 13, 2026: Thanks to everyone who participated in Challenge 15! The correct output for the alien alphabet is: ⪏⊚⊕⊟⊞⨙⊛∭↔⊠⊝৲⊣⊗⇲⊥⊢◉⊡⊤◴⚆⊜↪ 87 users got the right answer, out of 101 ...
- 177
60
votes
7k
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95
entries
Challenge #14: Signal from Noise [COMPLETED]
Update on January 8, 2026: Huge thanks to everyone who participated in the challenge. The conditions for signal/noise were tricky, and we appreciate the careful implementations! The correct sum of the ...
- 177
81
votes
7k
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71
entries
Challenge #13: Integer sorting in a grid [COMPLETED]
Update on October Dec 4: Huge thanks to everyone who participated in the challenge. The correct answer is that 45 of the sets were impossible to put into the grid. We received 70 responses from 68 ...
- 2,249
42
votes
5k
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9
entries
Challenge #12: Spooky Halloween scene [COMPLETED]
Update, Nov 13: Thanks to all that participated and voted in this challenge! In terms of votes, top 3 entries were: 1st place: Phil with a spooky house scene 2nd place: Death-is-the-real-truth (...
60
votes
5k
views
55
entries
Challenge #11: Taco crawl optimization [COMPLETED]
Update on October 23: Huge thanks to everyone who participated in the challenge. The correct routing was [0,7,5,6,2,10,4] for 97 tastiness and 2.8945 tastiness/distance. 43 of the 53 entries provided ...
-20
votes
6k
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57
entries
Challenge #10: Road safety challenge (joint with Kaggle) [COMPLETED]
Update, Nov 1, 2025: The challenge is now complete. Thanks to those that participated. We'll review the entries and soon announce the users that receive the badge. Kaggle is a platform for Machine ...
20
votes
4k
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30
entries
Challenge #9: Random Number Generator [COMPLETED]
Update: October 6, 2025: Thanks to everyone who participated in this challenge! It was very interesting to see the diverse approaches to random number generation. Congratulations to the following ...
27
votes
2k
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26
entries
Challenge #8: Word ladder [COMPLETED]
Update, October 2, 2025: Appreciation to everyone who participated in this challenge! The correct length of the word ladders is as follows: [stone, money] [11] [bread, crumb] [11] [smile, giant] [11] ...
- 245k
49
votes
3k
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96
entries
Challenge #7: Pangram checker [COMPLETED]
Update, October 2, 2025: A HUGE thanks to everyone who participated in this challenge! The correct answer is: 819 Non-Pangrams, 132 Pangrams (non-perfect) and 49 Perfect-Pangrams. We are very ...
- 379k
77
votes
7k
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130
entries
Challenge #6: Integer Counting [COMPLETED]
Update on October 8, 2025: Thanks to everyone who voted on the entries! We received 281 votes from 59 users. There were a lot of great responses to this challenge. We appreciate the participation. We'...
16
votes
3k
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4
entries
Challenge #5: Traffic Light Simulator [COMPLETED]
Congratulations to Kamran for the best response to this challenge! We were impressed by your simulation and also the inclusion of variable weather elements. This Challenge is now closed but entries ...
- 34.6k
49
votes
4k
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20
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Challenges Sandbox – Help us create new challenges
We are making some upgrades to Challenges – one of which is allowing users to contribute their own! If you have an idea for a challenge, please post it as an entry here in this Sandbox, where it can ...
37
votes
12k
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12
entries
Challenge #4: Create a futuristic technology [COMPLETED]
Awards for the fourth Stack Overflow code challenge: Most Upvotes: Davide Fiocco Vision Architect: 12Kittens New Contributor: Prakhar Agarwal All of the awards given (aside from most upvotes) are ...
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70
votes
12k
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54
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Challenge #3: Creating ASCII art snowflakes [COMPLETED]
Awards for the third Stack Overflow code challenge: Most Upvotes: André Serene Scene Creator: Ale_Bianco New Contributor: Michael Brown Most Customizable: FoxWise Snowflake Artisan: Newpzo All of the ...
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