The Curious Engineer

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CSE Blog

pratikpoddarcse.blogspot.com

Math, CS and quant puzzles for interview preparation - 300 classic brainteasers with solutions, sorted by topic and difficulty.

MathAlgorithms / data structures

’10’15’20’25
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303 from 26 Jun 2008 to 9 Oct 2026
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now and then (3 in the last year)
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2026 3

  1. Guessing a Two-Digit Number
  2. 100 Prisoners and 100 Boxes
  3. Bridge Crossing Puzzle

2017 2

  1. Fraction Brainteaser
  2. Buying Dimsums: The Chicken McNugget (Frobenius Number) Puzzle

2016 2

  1. Law of Large Numbers Failed
  2. Gold Links Puzzle

2015 7

  1. Soldiers in a Line
  2. Cheryl's Birthday Puzzle, Harder: Product, Sum and Difference Version
  3. Dividing Pizza with a Clock
  4. Buying in Rocket Ships and Selling in Fire Sale
  5. Box in Box problem
  6. Fibonacci Multiple Puzzle
  7. Gold Silver Numbers Puzzle

2014 19

  1. Maximum Number of Collinear Points
  2. Mathematics of SET game
  3. Broken Coffee Machine Puzzle: Expected Presses to Fill the Cup
  4. Pebble Placement Puzzle 2
  5. Pebble Placement Puzzle 1
  6. Diminishing Differences Puzzle
  7. Balancing Act Puzzle
  8. "Flawless Harmony" Puzzle
  9. Minimum sum of numbers in an array
  10. Caterer's Problem
  11. 3D Tic Tac Toe Puzzle: Count the Winning Lines in a 3x3x3 Cube
  12. Mad Robot Puzzle
  13. Social Network Friendship Paradox
  14. Expected length of Last Straw - Breaking the back of a camel
  15. Cards on a Square Turntable
  16. Cut the Polygon Puzzle - the solution will make you smile
  17. Estimate Pi Using Dice: A Quant Interview Puzzle
  18. (2n choose n) is never a perfect power
  19. Frobenius Coin Problem: Largest Amount You Cannot Pay with $a and $b

2013 41

  1. Determinant of Matrix (17-11)
  2. Open Ended Search Problem
  3. Picking K elements randomly
  4. Technical Interview Brain Teaser - IBM Ponder This - Neighbour Configuration
  5. Expected Flips Until HHTHHTT: Two-Coin Tossing Puzzle
  6. Calculus Limit Puzzle
  7. Weighing Problem - Discrete Mathematics Puzzle
  8. Discrete Mathematics Problem - Grouping Students
  9. Prime Power Math Puzzle
  10. Separate Odd and Even Numbers in an Array (Algorithm Puzzle)
  11. Chess 5 Piece Puzzle: Place the King, Queen, Rook, Bishop and Knight
  12. Number of Shortest Paths in an n x m Grid (Combinatorics Puzzle)
  13. Divisibility Problem
  14. Find Fixed Point (x[i]=i) in an Array
  15. Walking Ant Problem - Part 2
  16. Guide to Wall Street Quant Jobs for IITians
  17. Minimum Point in a Rotated Sorted Array
  18. Probability Puzzle: Expected Number of Expression Evaluations
  19. Combinatorics + Game Theory Puzzle
  20. Self Referential Problem - from "What would Martin Gardner Tweet"
  21. Edit Distance Problem
  22. Math Game of Zero String
  23. Math in Movies
  24. 5 Books for Quantitative Analyst Beginners
  25. Nine Digit Number - Math Puzzle
  26. Matrix Puzzle - Math Puzzle
  27. Art of Puzzle Solving
  28. Equations Puzzle
  29. Candy Game - Math Puzzle
  30. Black and White Squares Puzzle
  31. Penny Roll Puzzle
  32. Integer Points Puzzle: 5 Lattice Points Always Hide a Third
  33. 100-Sided Die Game: Take the Roll or Pay $1 to Re-roll (Jane Street)
  34. World Series Betting Puzzle: End Exactly $100 Up or Down
  35. Simple Divisor Problem - Math Puzzle
  36. Mad Hat Party
  37. Broken Clock Puzzle
  38. Probability Puzzle: Guess Position of Card
  39. Determinant of Binary Matrix
  40. Evenly Spaced Ones in Binary String
  41. Fermat's Last Theorem Puzzle: The 10-Year-Old Who Disproved the Claim

2012 39

  1. Romanian Informatics Olympiad - Modified Huffman Encoding
  2. Predict Your Partner's Coin: A 3-Player Strategy Puzzle
  3. Pizza Distribution Puzzle
  4. Most Popular Math Puzzles in 2012
  5. Snakes and Ladders Optimization
  6. Geometry Contruction - Bisect Areas of 2 Triangles
  7. Spy Control Problem - Peter Winkler
  8. Hanging Picture Puzzle
  9. Multilingual Hedge Fund - Combinatorics Puzzle
  10. European Peg Solitaire Solvability
  11. Geometry Puzzle: Crush the Rebellion
  12. Geometry Problem : Line of Sight
  13. Sam Loyd Puzzle Solvability
  14. Math Olympiad Problem - Milk Distribution
  15. Quick Probability Questions for Interviews
  16. Geometry Puzzle: Center of Square in Circle
  17. Math Olympiad Problem : Overlapping Coins
  18. Number of 1s in 2's complement representation
  19. Hourglass Puzzle: Measure 9 Minutes with 4- and 7-Minute Hourglasses
  20. Strategy Game - Similar to Nim
  21. USA Maths Olympiad Problem - 200th Puzzle
  22. IQ Measurement Puzzle - Statistics Problem
  23. Inequality Problem
  24. Brownian Motion in Circles Puzzle
  25. Arithmetic Puzzle: Broken Calculator
  26. IBM Ponder This July 2012 - Colouring Balls
  27. Pairwise Product Set Cardinality
  28. Why Flights Don't Fly Straight: New York to Mumbai Great Circle Puzzle
  29. Permutations and Combinations Puzzle: Cube with Equal Faces
  30. Scheduling Problem
  31. Original Puzzle: Pattern Lock - Combinatorics Puzzle - Number of Possible Passwords
  32. Maximum Family of Subsets Intersecting in Exactly One Element
  33. Lion and Man in a Circular Cage: Can the Lion Catch the Tamer?
  34. Algorithm Puzzle: Triplets in Array
  35. Original Problem : ATM Money Withdrawal Puzzle
  36. Lazy Walking Strategy Puzzle
  37. Number Board Puzzle: Sum of Colours
  38. Pile Puzzle
  39. Digit Permutation Puzzle

2011 43

  1. Number of digits in 125^100
  2. Array Problems - Contiguous Sum and Distinct Elements
  3. Crossing the Road
  4. Shortest Curve dividing Equilateral Triangle
  5. Matrix Saddle Points
  6. Rubik's Cube
  7. Linked List Delete
  8. Numbers on a circle - Minimum sum of consecutive differences
  9. 21 Problems in 21 Days left for Placements
  10. Guess 3 numbers
  11. Scaling a Square
  12. Divisibility of 111...1111
  13. Sphagetti Breakfast
  14. Distinct numbers in a sample draw
  15. Function Inner Product
  16. Difference between foo(void) and foo()
  17. C code 32 bit vs 64 bit
  18. C++ Macro Concatenation
  19. Arrange in a Sequence
  20. Football Board
  21. Sacred Right Pan - IMO 2011 Problem
  22. Increasing Sequence in Dice
  23. Expectation of Max Frequency
  24. Coin Chain Reaction
  25. Moscow Math Olympiad Problems
  26. Coloured Run of Cards
  27. Bad BarCode
  28. Wrong Solution
  29. Need for Needles
  30. Smallest Number in Decreasing Sequence
  31. Keynesian beauty contest
  32. Dividing a Plane
  33. King's Poisonous Wine II: 500 Barrels, 4 Prisoners, 48 Hours
  34. Coin Toss Bankruptcy
  35. Derangement - Complete FAIL!
  36. Equal Heads and Tails: The Expected Number of Tosses (Coin Puzzle)
  37. Comparison without relational operators
  38. Sum of 2001 powers of digits
  39. Expectation of 2^(Cycle Length)
  40. CMU Puzzle Toad: Abduction
  41. Car Problem
  42. Birthday Game Puzzle: Where to Stand in Line to Win a Free Ticket
  43. Expected number of draws

2010 80

  1. Water Jug Problem
  2. Equal zeroes and ones
  3. Locks and Switches
  4. Order of cards
  5. Stick Broken Into Three Pieces
  6. The Social Network (2010) - FaceMash Algorithm
  7. Probability of Grade A or B
  8. Sorted arrays
  9. Coin Tossing - Lucky Dealer
  10. Optimal Trading Execution
  11. Number of Colour Changes
  12. Random Walk around Square
  13. Two creepers climbing a tree
  14. Number of Rounds of Derangements
  15. Baseball Party
  16. Equilateral Triangle Division
  17. Painting Coloured Balls
  18. Senators and Graph Theory: Committee Splitting with 3 Enemies Each
  19. Coin Balancing
  20. Randomized Ice Cream
  21. Prime Number Strategy Game
  22. Number Games
  23. Equal numbers in a circle
  24. Conway's Soldiers (CheckerBoard Unreachable Line)
  25. Magic Money Machine
  26. Number of Sons
  27. Puzzle on Sorting
  28. Hats and Rooms
  29. Coin conundrum
  30. Differing views
  31. Coin Sequence Game
  32. Cube in a sphere
  33. Russian Coins
  34. Tip the Balance
  35. Mathematics of Housie/Tambola
  36. City Planning
  37. Veit Elser’s Formidable 14
  38. Another Hat Problem
  39. Oleg Kryzhanovsky’s Problem - Coin Sequence
  40. Weighing Puzzle: 13 Piles of Coins, One Counterfeit Pile
  41. Sleeping Beauty Paradox
  42. Street Watch
  43. Unexpectedly Great Expections
  44. 100 Locomotives Problem
  45. Sink the Submarine
  46. Traffic Jam
  47. Real Expensive Pills
  48. Perfect Powers: Print All m^n up to N in Order (Programming Puzzle)
  49. Sweet Heart Mix Tape
  50. Coin Weighing Problem
  51. Drunk Guests
  52. Pebble Piles
  53. Asking a girl out
  54. Checkers Problem
  55. Invert the Cups
  56. Fair Hat Game
  57. Red vs Black cards - Expected payoff
  58. Three NOT Gates from Two NOT Gates
  59. Hungry Lion
  60. IBM Ponder This January 2010 Puzzle
  61. Math Olympiad Problems
  62. Brave Warrior
  63. Bottom Dollar
  64. Give and Take
  65. Horse Race
  66. Hats in a circle
  67. Homo paradox
  68. Duplicate Integer
  69. Cap Puzzle (Infinite version)
  70. Indian Sudoku Championship 2010
  71. Card Shuffle
  72. Two envelopes Problem
  73. Dont roll more
  74. Correct Letters
  75. Coupon Collector Problem
  76. Infected Chessboard
  77. Chessboard Circle
  78. Capturing a pirate ship
  79. Threaded Pins
  80. Finding a Hermit: The Five Holes in a Line Puzzle

2009 63

  1. Top Card
  2. Uniform Candy Distribution
  3. Gaadi chalao
  4. Fate of Ships
  5. The Best Horse
  6. Kirkman's schoolgirl problem
  7. Empty Bucket
  8. Catch me if you can?
  9. Dividing gold into parts
  10. Infinity Problem
  11. Ant Collision
  12. Weird Number Sequence
  13. Number of Locks and Keys
  14. Expected Number of HH
  15. Generate a Uniform Random Point in a Circle (Interview Puzzle)
  16. Break the sticks
  17. Ants on a Cube
  18. Placements and Puzzles!!!
  19. Nearest Point problem
  20. Blind flipping
  21. Missing Digit
  22. Polya's Urn Problem: Expected Balls in the Smaller Urn
  23. Flipping Bits in a Matrix
  24. Lets Call 50
  25. Minimum and Maximum
  26. Weighing problems
  27. Choose the maximum of two number
  28. Cyclic Strings
  29. Four Ants - HC Verma
  30. Chicken Nuggets
  31. IBM Ponder This November Challenge
  32. Wikipedia Links for Algorithms and Probability
  33. No division operator and O(n)
  34. Another Coin Problem
  35. Coins Puzzle
  36. IBM Ponder This Puzzle
  37. Technician from IIT
  38. King's Poisonous Wine
  39. Find your number
  40. Another Hat Puzzle
  41. See a car
  42. Tukde tukde
  43. Expected Tosses for Consecutive Heads: 2 Heads vs 3 Heads Puzzle
  44. Expected Value
  45. Mean minimum distance for N random points on a one-dimensional line
  46. 9 balls
  47. Bulb Puzzle
  48. Walking Ants
  49. Losing at Dice
  50. Shoot me!!
  51. Bol Baby Bol
  52. 25 Horses, 5 Tracks: Find the Top 3 in the Fewest Races
  53. Semi-circle covering n points : Puzzle
  54. The King's salary
  55. Josephus Problem - Puzzle
  56. Five Thieves and Bounty
  57. Game of Two
  58. Cap Puzzle
  59. Puzzle: Working Computer
  60. Puzzle: What's the number on my Hat?
  61. India and Open Source Software Part-2
  62. Amazing Boy Girl Paradox
  63. Open Source is a Must for India

2008 4

  1. The ring of Numbers
  2. Limitation of a data structure
  3. Fibonacci Sequence
  4. Steve Jobs in his own words