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List · 75 problems

Blind 75: All 75 Problems in a Study Order

Seventy-five problems you can explain beat seventy-five you copied. The order is mine. I start with the openers, then go one topic at a time, easiest first.

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Whose list this is

Yangshun Tay put the Blind 75 together. StrongYes did not write it, and the problems belong to their sources. Every problem below opens a StrongYes practice page for the problem with the same name. Source: Tech Interview Handbook: best practice questions.

The problems, in my order

19 easy · 49 medium · 7 hard. Solved marks come from this browser and, signed in, your account.

  1. Contains DuplicateeasyArrays & Hashing
  2. Valid AnagrameasyStringsArrays & Hashing
  3. Two SumeasyTwo PointersArrays & Hashing
  4. Valid PalindromeeasyTwo PointersStrings
  5. Group AnagramsmediumStringsArrays & Hashing
  6. Product of Array Except SelfmediumArrays & Hashing
  7. Rotate ImagemediumArrays & Hashing
  8. Set Matrix ZeroesmediumArrays & Hashing
  9. Spiral MatrixmediumArrays & Hashing
  10. 3SummediumTwo PointersArrays & Hashing
  11. Valid ParentheseseasyStackStrings
  12. Find Minimum in Rotated Sorted ArraymediumBinary SearchArrays & Hashing
  13. Search in Rotated Sorted ArraymediumBinary SearchArrays & Hashing
  14. Best Time to Buy and Sell StockeasySliding WindowArrays & Hashing
  15. Analytics: Longest Unique Session WindowmediumSliding WindowStrings
  16. Longest Repeating Character ReplacementmediumSliding WindowTwo Pointers
  17. Minimum Window SubstringhardSliding WindowStrings
  18. Linked List CycleeasyLinked ListsTwo Pointers
  19. Merge Two Sorted ListseasyLinked Lists
  20. Reverse Linked ListeasyLinked Lists
  21. Remove Nth Node From End of ListmediumLinked ListsTwo Pointers
  22. Reorder ListmediumLinked ListsStack
  23. Implement Trie (Prefix Tree)mediumTreesDesign
  24. Invert Binary TreeeasyTreesBFS & DFS
  25. Maximum Depth of Binary TreeeasyTreesBFS & DFS
  26. Same TreeeasyTreesBFS & DFS
  27. Subtree of Another TreeeasyTreesStrings
  28. Binary Tree Level Order TraversalmediumTreesBFS & DFS
  29. Construct Binary Tree from Preorder and Inorder TraversalmediumTreesBFS & DFS
  30. Design Add and Search Words Data StructuremediumTreesDesign
  31. Kth Smallest Element in a BSTmediumTreesBFS & DFS
  32. Lowest Common Ancestor of a Binary Search TreemediumTreesBFS & DFS
  33. Validate Binary Search TreemediumTreesBFS & DFS
  34. Serialize and Deserialize Binary TreehardTreesDesign
  35. Telemetry: Top K Frequent Error CodesmediumHeapsArrays & Hashing
  36. Find Median from Data StreamhardHeapsTwo Pointers
  37. Merge K Sorted ListshardLinked ListsHeaps
  38. Combination SummediumBacktrackingArrays & Hashing
  39. Word SearchmediumBacktrackingStrings
  40. Word Search IIhardBacktrackingTrees
  41. Clone GraphmediumGraphsBFS & DFS
  42. Course SchedulemediumHeapsGraphs
  43. Graph Valid TreemediumGraphsBFS & DFS
  44. Longest Consecutive SequencemediumGraphsArrays & Hashing
  45. Number of Connected Components in an Undirected GraphmediumGraphsBFS & DFS
  46. Number of IslandsmediumGraphsBFS & DFS
  47. Pacific Atlantic Water FlowmediumGraphsBFS & DFS
  48. Alien DictionaryhardGraphsStrings
  49. Climbing StairseasyDynamic Programming
  50. Coin ChangemediumDynamic ProgrammingBFS & DFS
  51. Decode WaysmediumDynamic ProgrammingStrings
  52. House RobbermediumDynamic ProgrammingArrays & Hashing
  53. House Robber IImediumDynamic ProgrammingArrays & Hashing
  54. Longest Common SubsequencemediumDynamic ProgrammingStrings
  55. Longest Increasing SubsequencemediumBinary SearchDynamic Programming
  56. Longest Palindromic SubstringmediumTwo PointersDynamic Programming
  57. Maximum Product SubarraymediumDynamic ProgrammingArrays & Hashing
  58. Maximum SubarraymediumDynamic ProgrammingArrays & Hashing
  59. Palindromic SubstringsmediumTwo PointersDynamic Programming
  60. Unique PathsmediumDynamic Programming
  61. Word BreakmediumTreesDynamic Programming
  62. Binary Tree Maximum Path SumhardTreesDynamic Programming
  63. Container With Most WatermediumGreedyTwo Pointers
  64. Jump GamemediumGreedyDynamic Programming
  65. Meeting RoomseasyIntervalsGreedy
  66. Insert IntervalmediumIntervalsArrays & Hashing
  67. Meeting Rooms IImediumIntervalsGreedy
  68. Merge IntervalsmediumIntervalsArrays & Hashing
  69. Non-overlapping IntervalsmediumIntervalsGreedy
  70. Counting BitseasyBit ManipulationDynamic Programming
  71. Missing NumbereasyBit ManipulationBinary Search
  72. Number of 1 BitseasyBit Manipulation
  73. Reverse BitseasyBit Manipulation
  74. Sum of Two IntegersmediumBit Manipulation
  75. Encode and Decode StringsmediumDesignStrings

How I'd work it

  1. 1

    Start with the openers

    Contains Duplicate, Valid Anagram and Two Sum teach one habit: remember what you have already seen.

  2. 2

    Go one topic at a time

    Do two or three problems on a topic, then move on. Come back to the ones that went worst.

  3. 3

    Explain before you move on

    Say the idea, the cost and one edge case out loud. If you cannot, the problem is not done.

Two problems a day, five days a week, finishes this list in about 8 weeks.

The list by pattern

Every problem is a costume over a smaller idea. Learn the idea and the costume stops mattering.

Where Coco comes in

Coco is an AI study partner, not a person. She listens while you explain your code, asks what a line does and never hands you the fix. Sign in free to type with Coco, up to a daily limit, and to talk with her for one hour. After that, talking comes with the $79 pack. Anyone can open the editor and run their code.

Questions people ask

How long does the Blind 75 take?
Two problems a day, five days a week, takes about eight weeks. Fewer per day stretches it, and that is fine.
Is the Blind 75 enough for a coding interview?
It covers the core patterns, not every question. Learn the pattern behind each problem, then practice new ones.
Do I have to follow this order?
No. The order is mine, built to introduce topics gently. Skip ahead when you know a weak area.
Is the Blind 75 free on StrongYes?
The editor and the code runner are free for every problem. The pricing page says what Coco costs and when.

Keep going

Fin and Coco are characters, not people. strongyes.io is independent. Leo builds it with AI agents.