The problem collection "109 Python Problems for CCPS 109" is now complete, and no further problems will ever be added to this collection. In addition to the actual problems, each of the three problem collections here includes fourteen bonus problems intended for students who are looking for a serious challenge. For personal reasons, it is extremely important to me that all these bonus problem specifications and their private model solutions contain no bugs, so that the checksums hardcoded in the automated tester are true and achievable by everyone who chooses to work hard to solve these problems. The first student to send me working solution to each problem gets their name etched forever into the bounty table below.
| Problem | Bounty claimed |
| 110: Reverse the Rule 110 | Karel Tutsu, October 22, 2022 |
| 111: Aye, eye, I | John Hodgins, April 17, 2023 |
| 112: Count domino tilings | Maxim Olatoye, July 8, 2023 |
| 113: Invaders must die | |
| 114: Stepping stones | Alan Pangnathip, Nov 21, 2022 |
| 115: Ex iudiciis, lux | Thomas Brooks, February 15, 2026 |
| 116: Flatland golf | Dennis Kaydalov, Nov 2, 2023 |
| 117: TextmirrororrimtxeT | "George Hotz", October 24, 2022 |
| 118: Hy-phen-a-tion by com-pu-ter | Cindy Hua, November 13, 2022 |
| 119: Jealous vs. zealous | GPT-4, March 28, 2023 |
| 120: Count the permorsetations | George Zhang, October 30, 2022 |
| 121: Count your lucky sevens | Felix Nguyen, Dec 18, 2022 |
| 122: Forks on the Gin Lane | Rimma Konoval, Jun 21, 2024 |
| 123: One, two, three, grow old with me | |
| A110: String stretching | |
| A111: Casinos hate this Toronto man! | |
| A112: Word bin packing | Dan Ruiyot, April 13, 2025 |
| A113: Probabilistic tic-tac-toe | Thomas Brooks, February 2, 2026 |
| A114: Bandwidth minimization | Mojtaba Khalesi, March 31, 2025 |
| A115: Set splitting | Ethan Harriman, March 19, 2025 |
| A116: Domino poppers | Dan Ruiyot, April 13, 2025 |
| A117: Knight jam | Dan Ruiyot, April 13, 2025 |
| A118: Cubes on the trailer | |
| A119: Tom and Jerry | Ekrem Yilmaz, March 28, 2025 |
| A120: Pinch to a pound | Thomas Brooks, February 16, 2026 |
| A121: Minimal Egyptian fractions | Fardin Islam, April 13, 2025 |
| A122: Unity partition | |
| A123: Ants on the rod | |
| T110: The way of a man with array | |
| T111: Levine's sequence | Thomas Brooks, January 20, 2026 |
| T112: Post correspondence problem | Thomas Brooks, January 27, 2026 |
| T113: Optimal bridge placement | |
| T114: No dogs, no masters | |
| T115: Car match game | |
| T116: Liquid sort | |
| T117: Count bowling paths | |
| T118: Expiring cookies | Thomas Brooks, February 9, 2026 |
| T119: Sonata pattern matching | |
| T120: Fox and hounds | |
| T121: Toads and frogs | |
| T122: Unamerican gladiators | |
| T123: Life is like a box of dominoes |
Starting March 2023, the author started creating another set of Python problems, separate from the main corpus of the 109 Python Problems. (One can only quit for so long without the inevitable relapse.) Here are the students who first sent me the working solution for each particular problem.
| Problem | Bounty claimed |
| 1. The Fischer King | Karel Tutsu, June 7, 2023 |
| 2. Multiplicative persistence | Karel Tutsu, June 7, 2023 |
| 3. Top of the swops | Karel Tutsu, June 7, 2023 |
| 4. Lowest common dominator | |
| 5. Discrete rounding | Karel Tutsu, June 7, 2023 |
| 6. Translate | Zoe Lebel-Pantazopoulos, August 4, 2024 |
| 7. Ifs and butts | Zoe Lebel-Pantazopoulos, August 4, 2024 |
| 8. Word positions | |
| 9. Power prefix | |
| 10. Deterministic finite automata | Kiran Soogrim-Maharaj, August 6, 2024 |
| 11. The parking lot is full | Aryan Khurram, August 6, 2024 |
| 12. Lychrel numbers | Zoe Lebel-Pantazopoulos, August 4, 2024 |
| 13. Powertrain | |
| 14. First fit bin packing | |
| 15. Count possible triangles | Kiran Soogrim-Maharaj, August 6, 2024 |
| 16. Arrow walk with me | Aryan Khurram, August 6, 2024 |
| 17. Count Friday the Thirteenths | Kiran Soogrim-Maharaj, August 6, 2024 |
| 18. Median filter | Kiran Soogrim-Maharaj, August 6, 2024 |
| 19. The magic knight of Muhammad ibn Muhammad | |
| 20. Man of La Cancha | |
| 21. Nondeterministic finite automata | Kiran Soogrim-Maharaj, August 6, 2024 |
| 22. Count unicolour rectangles | |
| 23. Count palindromic substrings | Karel Tutsu, June 13, 2023 |
| 24. Longest mirrored substring | Kiran Soogrim-Maharaj, August 6, 2024 |
| 25. Square lamplighter | |
| 26. Pairwise lamps | |
| 27. Accumulating merge | Aryan Khurram, August 6, 2024 |
| 28. And they walk in twos or threes or more | |
| 29. Ladies and gentlemen, Conway Bitty | |
| 30. Lowest fraction between two fractions | |
| 31. Reasonable filename comparison | Anonymous, July 8, 2023 |
| 32. List the Langford violations | Anonymous, July 8, 2023 |
| 33. Ten pins, not six, Dolores | Karel Tutsu, June 7, 2023 |
| 34. Strict majority element | Maxim Olatoye, May 20, 2023 |
| 35. Add like an Egyptian | |
| 36. Sorting by pairwise swaps | |
| 37. Van der Corput sequence | |
| 38. Maximal repeats | |
| 39. It's a game, a reflection | Karel Tutsu, June 11, 2023 |
| 40. Reverse a Fibonacci-like sequence | |
| 41. Recamán sequence | |
| 42. Mian–Chowla sequence | Karel Tutsu, June 12, 2023 |
| 43. Stern–Brocot path | |
| 44. Carryless multiplication | |
| 45. Mū tōrere boom-de-ay | |
| 46. A place for everything and everything in its place | |
| 47. Scoring a tournament bridge hand | |
| 48. Manimix | Aryan Khurram, August 4, 2024 |
| 49. Count distinct substrings | |
| 50. Replacement with perfect hindsight | Aryan Khurram, August 5, 2024 |
| 51. Replacement with perfect foresight | |
| 52. When there's no item, there's no problem | Karel Tutsu, August 30, 2023 |
| 53. Boxed away | |
| 54. ’Tis but a scratch | |
| 55. Do or die | |
| 56. Arithmetic skip | |
| 57. Carving Egyptian fractions | |
| 58. Largest square of ones | Maxim Olatoye, June 15, 2023 |
| 59. Infection affection | |
| 60. Prize strings | |
| 61. String shuffle | Aryan Khurram, August 5, 2024 |
| 62. Weak Goodstein sequence | |
| 63. Markov distance | |
| 64. A very graphy caterpillar | |
| 65. St. Bitus‘ Dance | |
| 66. Digit string partition | |
| 67. Hofstadter's figure-figure sequences | |
| 68. [Be]t[Te]r [C][Al]l [Sm][Al]l | |
| 69. Spiral matrix | |
| 70. Baker–Norine dollar game | Samuel Hua, March 10, 2025 |
| 71. Total covered area | Karel Tutsu, September 1, 2023 |
| 72. Balsam for the code | Nam Nguyen, March 6, 2024 |
| 73. Flip those trips | |
| 74. Maximal disk placement | Sarvesh Badhwar, March 13, 2025 |
| 75. Nice sequence | Ethan Harriman, February 22, 2025 |
| 76. Forbidden digit | Zhiyu Jin, April 4, 2025 |
| 77. Decoding the base –1 + i | |
| 78. Independent dominating set | Mohamed Shrief, March 28, 2025 |
| 79. Vertex cover | |
| 80. Shotgun sequence | |
| 81. Card row game | Maxim Olatoye, June 18, 2023 |
| 82. The remains | |
| 83. Count sublists with odd sums | Karel Tutsu, August 30, 2023 |
| 84. Tailfins and hamburgers | Nam Nguyen, March 30, 2024 |
| 85. Split the digits, maximize the product | |
| 86. Tower of cubes | Nam Nguyen, March 6, 2024 |
| 87. Gijswijt sequence | |
| 88. Sum of consecutive squares | Karel Tutsu, August 30, 2023 |
| 89. Balance of power | Samuel Hua, March 10, 2025 |
| 90. Longest zigzag subsequence | |
| 91. Kimberling's expulsion sequence | Nam Nguyen, April 26, 2024 |
| 92. Kimberling's repetition-resistant sequence | Nam Nguyen, May 1, 2024 |
| 93. Game with multiset | Nam Nguyen, April 26, 2024 |
| 94. Tower of Babel | Nam Nguyen, March 6, 2024 |
| 95. Make a list self-describing | Nam Nguyen, May 1, 2024 |
| 96. Two pins, not three, Dolores | Matt Campeau, April 2, 2024 |
| 97. Out where the buses don't run | “Shwnzp”, May 26, 2023 |
| 98. SMETANA interpreter | Abdul Rahman Al Nabulsi, April 15, 2024 |
| 99. The sharpest axes | Nam Nguyen, April 24, 2024 |
| 100. Vidrach Itky Leda | Nam Nguyen, May 1, 2024 |
| 101. How's my coding? Call 1-800-3284778 | Karel Tutsu, August 25, 2023 |
| 102. Scatter her enemies | Karel Tutsu, March 8, 2023 |
| 103. Sneaking | |
| 104. Inverse pair sums | |
| 105. Blocking pawns | Nam Nguyen, March 6, 2024 |
| 106. Boggles the mind | Mortreza Eivazi, June 30, 2023 |
| 107. The round number round | Shane Liu, March 31, 2024 |
| 108. Complete a Costas array | Karel Tutsu, August 22, 2023 |
| 109. Oppenhoppenheimereimer | John Hodgins, April 20, 2023 |
A third problem collection was started August 2024, and it was completed to also contain 109 + 14 = 123 problems in January 31, 2026. Here are the students who first sent me a working solution to each problem.
| Problem | Bounty claimed |
| 1. Multiply and sort | Thomas Brooks, January 18, 2026 |
| 2. Approval voting | Thomas Brooks, January 18, 2026 |
| 3. Vigenère cipher | Thomas Brooks, January 18, 2026 |
| 4. Once you go down, you can't come up again | |
| 5. Baum–Sweet sequence | |
| 6. Damm those errors | Thomas Brooks, January 22, 2026 |
| 7. Tanton necklace | Thomas Brooks, February 6, 2026 |
| 8. Bug in a line | Thomas Brooks, January 19, 2026 |
| 9. Friendship paradox | Thomas Brooks, January 19, 2026 |
| 10. Right turn at Albuquerque | Thomas Brooks, January 19, 2026 |
| 11. Generalized Fibonacci sequence | Thomas Brooks, January 19, 2026 |
| 12. Pollard's rho integer factorization | |
| 13. Bays–Durham shuffle | Thomas Brooks, January 27, 2026 |
| 14. Double-ended pop | Thomas Brooks, January 20, 2026 |
| 15. First singleton | Thomas Brooks, January 20, 2026 |
| 16. Candy sharing game | Thomas Brooks, January 27, 2026 |
| 17. Haar wavelet transform: Encode | Thomas Brooks, January 27, 2026 |
| 18. Haar wavelet transform: Decode | |
| 19. Shell sort | Thomas Brooks, January 22, 2026 |
| 20. Mixed type sorting | Thomas Brooks, January 20, 2026 |
| 21. The nine lives of Meaowsephus | Thomas Brooks, January 20, 2026 |
| 22. Maximum repeated suffix | |
| 23. Count slices with given sum | Thomas Brooks, January 25, 2026 |
| 24. First sublist whose sum is some multiple of k | |
| 25. Ones mule, zeros pool | Thomas Brooks, January 27, 2026 |
| 26. The backwards god | |
| 27. Klee's measure problem | |
| 28. Poker test of randomness | Thomas Brooks, January 27, 2026 |
| 29. Three-way partition | Thomas Brooks, February 6, 2026 |
| 30. Primality buildup | Thomas Brooks, January 25, 2026 |
| 31. Goldbach verification | Thomas Brooks, January 25, 2026 |
| 32. A square and twice a prime | |
| 33. Pseudo-Smarandache function | |
| 34. Conway's subprime sequence | |
| 35. Rowland's prime pump | Thomas Brooks, January 27, 2026 |
| 36. Lehmer code: encoding | |
| 37. Sum of square roots | Thomas Brooks, February 2, 2026 |
| 38. Night shift | |
| 39. Infinite self-square integer | Thomas Brooks, January 23, 2026 |
| 40. Strahler numbers | |
| 41. Loopless walk | |
| 42. Maximum number of blocks during shutdown | |
| 43. List of all factors | |
| 44. Fourth seat opening | |
| 45. Convert a fraction to a simple continued fraction | Thomas Brooks, February 6, 2026 |
| 46. Convert a simple continued fraction to a fraction | |
| 47. Sturm und drangle | |
| 48. Rational roots of a polynomial | |
| 49. Multiple winner election | Thomas Brooks, February 6, 2026 |
| 50. Spiral walk | |
| 51. Equal sum partition | |
| 52. Maximum interval clique | |
| 53. Maximum overlap intervals | |
| 54. Split at None | Karel Tutsu, August 30, 2024 |
| 55. Chunk sorting | |
| 56. Merge the two biggest | |
| 57. Lehmer code: decoding | |
| 58. Bayesian updating of dice | |
| 59. Haircut | Thomas Brooks, January 20, 2026 |
| 60. Kadane in triplicate | |
| 61. Yellowstone sequence | |
| 62. Largest rectangle in histogram | |
| 63. Frobenius nuggets | |
| 64. Postage stamp problem | |
| 65. Knaves of the round table | |
| 66. Six of this, half a dozen of the other | |
| 67. Factoradical dudes | Thomas Brooks, February 6, 2026 |
| 68. Tarjan's strongly connected components | |
| 69. Copeland harder | Thomas Brooks, February 24, 2026 |
| 70. Instant runoff voting | |
| 71. Cousin explainer | |
| 72. One-dimensional random walk | |
| 73. Knight watch | |
| 74. Longest Fibonacci-like subsequence | |
| 75. Maximize exam confusion | |
| 76. Burrows–Wheeler transform | |
| 77. Bron–Kerbosch maximal clique enumeration | |
| 78. Queue jockeys | |
| 79. Distance from land | |
| 80. Smallie Bigs | |
| 81. Gauss circle | |
| 82. Zeckendorf decoding | Thomas Brooks, January 20, 2026 |
| 83. Sultan's daughter | |
| 84. Limited swap sorting | |
| 85. Average run length test of randomness | Thomas Brooks, January 27, 2026 |
| 86. Count increasing paths | |
| 87. Cocke–Younger–Kasami parsing | |
| 88. Avoidant subset of points on a circular line | |
| 89. Ehrenfeucht–Mycielski sequence | |
| 90. Diamond sequence | |
| 91. Minimize largest triangle | |
| 92. Cutting sticks | |
| 93. Optimal text filling | |
| 94. S-expression evaluator | Thomas Brooks, January 20, 2026 |
| 95. Expand recursively run-length encoded string | Thomas Brooks, January 20, 2026 |
| 96. Longest common strictly increasing subsequence | |
| 97. Maximum palindromic integer | |
| 98. Optimal palindromic split | |
| 99. Semiconnected guys | Thomas Brooks, February 19, 2026 |
| 100. Falling squares | |
| 101. Tchuka Ruma | |
| 102. Slater–Vélez sequence | |
| 103. Odds and evens | Thomas Brooks, June 18, 2025 |
| 104. The prodigal sequence | |
| 105. Descending suffix game | |
| 106. The Borgesian dictionary | Thomas Brooks, February 23, 2026 |
| 107. The Dictorian borgesitory | |
| 108. The art of strategic sacrifice | |
| 109. Colonel Blotto and the Spymaster |