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D3

Hashing

48 stations · 19h

Hash maps and sets for counting, lookup and dedup. 48 interview problems explained by codestorywithMIK (19h of video), grouped into 6 patterns such as Frequency Counting, Two Sum Style Lookup, Prefix Sum + HashMap.

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problems by zone (pattern)
  • Frequency Counting30
  • Two Sum Style Lookup11
  • Prefix Sum + HashMap4
  • Grouping & Canonical Keys2
  • Set Membership & Dedup5
  • Hash Design1

  1. Frequency Counting

    0 of 30 passed
  2. Find Players With Zero or One LossesLC 2225 · 15:55
    MediumGoogle · IndeedLeetCode ↗ (opens in a new tab)
  3. Unique Number of OccurrencesLC 1207 · 12:19
    EasyGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)
  4. Binary Trees With FactorsLC 823 · 32:32
    MediumGoogle · AmazonLeetCode ↗ (opens in a new tab)
  5. Count Nice Pairs in an ArrayLC 1814 · 17:55
    MediumGoogle · Meta · +3 more companiesLeetCode ↗ (opens in a new tab)
  6. Minimum Number of Pushes to Type Word I and IILC 3014 · 31:28
    EasyGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  7. Hand of StraightsLC 846 · 18:32
    MediumGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)
  8. Count Number of Bad PairsLC 2364 · 28:45
    MediumGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  9. Minimum Index of a Valid SplitLC 2780 · 33:57
    MediumGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)
  10. Rabbits in ForestLC 781 · 28:31
    MediumGoogle · Amazon · +6 more companiesLeetCode ↗ (opens in a new tab)
  11. Total Characters in String After Transformations ILC 3335 · 23:30
    MediumGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  12. Longest Palindrome by Concatenating Two Letter WordsLC 2131 · 17:35
    MediumGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)
  13. Bitwise ORs of SubarraysLC 898 · 25:59
    MediumGoogle · Amazon · +5 more companiesLeetCode ↗ (opens in a new tab)
  14. Vowel SpellcheckerLC 966 · 28:22
    MediumGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)
  15. Next Greater Numerically Balanced NumberLC 2048 · 35:43
    MediumGoogle · Meta · +3 more companiesLeetCode ↗ (opens in a new tab)
  16. Count Special TripletsLC 3583 · 33:43
    MediumGoogle · Meta · +1 more companiesLeetCode ↗ (opens in a new tab)
  17. Count Covered BuildingsLC 3531 · 30:03
    MediumGoogle · AmazonLeetCode ↗ (opens in a new tab)
  18. Maximum Square Area by Removing Fences From a FieldLC 2975 · 32:50
    MediumGoogle · BloombergLeetCode ↗ (opens in a new tab)
  19. Check if Strings Can be Made Equal With Operations I and IILC 2839 · 30:44
    EasyGoogle · Microsoft · +1 more companiesLeetCode ↗ (opens in a new tab)
  20. Minimum Distance Between Three Equal Elements I and IILC 3741 · 27:17
    EasyGoogle · AmazonLeetCode ↗ (opens in a new tab)
  21. Closest Equal Element QueriesLC 3488 · 23:18
    MediumGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  22. Count the Number of Special Characters IILC 3121 · 14:27
    MediumGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)
  23. Find the Maximum Number of Elements in SubsetLC 3020 · 35:13
    MediumGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)
  24. Destination CityLC 1436 · 8:58
    EasyAmazon · Meta · +2 more companiesLeetCode ↗ (opens in a new tab)
  25. Path CrossingLC 1496 · 8:57
    EasyGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)
  26. Redistribute Characters to Make All Strings EqualLC 1897 · 18:37
    EasyMoengageLeetCode ↗ (opens in a new tab)
  27. Count the Number of Consistent StringsLC 1684 · 14:34
    EasyGoogle · Bloomberg · +1 more companiesLeetCode ↗ (opens in a new tab)
  28. Minimum Operations to Make Array Values Equal to KLC 3375 · 20:02
    EasyGoogle · Microsoft · +2 more companiesLeetCode ↗ (opens in a new tab)
  29. Find Lucky Integer in an ArrayLC 1394 · 39:00
    EasyGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)
  30. Coupon Code ValidatorLC 3606 · 18:01
    EasyGoogle · MetaLeetCode ↗ (opens in a new tab)
  31. N-Repeated Element in Size 2N ArrayLC 961 · 24:19
    EasyGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)

  32. Two Sum Style Lookup

    0 of 11 passed
  33. Equal Row and Column PairsLC 2352 · 19:59
    MediumGoogle · Meta · +3 more companiesLeetCode ↗ (opens in a new tab)
  34. Number of Good PairsLC 1512 · 15:34
    EasyGoogle · Amazon · +6 more companiesLeetCode ↗ (opens in a new tab)
  35. Restore the Array From Adjacent PairsLC 1743 · 20:31
    MediumGoogle · Amazon · +7 more companiesLeetCode ↗ (opens in a new tab)
  36. Count Nice Pairs in an ArrayLC 1814 · 17:55
    MediumGoogle · Meta · +3 more companiesLeetCode ↗ (opens in a new tab)
  37. Array Pair Sum Divisibility Problem27:41
    LeetCode ↗ (opens in a new tab)
  38. Check If Array Pairs Are Divisible by kLC 1497 · 24:00
    MediumGoogle · Amazon · +5 more companiesLeetCode ↗ (opens in a new tab)
  39. Count Number of Bad PairsLC 2364 · 28:45
    MediumGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  40. Minimum Pair Removal to Sort Array IILC 3510 · 1:02:31
    HardGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)
  41. Minimum Absolute Distance Between Mirror PairsLC 3761 · 11:05
    MediumGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)
  42. Evaluate the Bracket Pairs of a StringLC 1807 · 22:18
    MediumGoogle · RemitlyLeetCode ↗ (opens in a new tab)
  43. Number of Equivalent Domino PairsLC 1128 · 25:35
    EasyGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)

  44. Prefix Sum + HashMap

    0 of 4 passed
  45. Check If Array Pairs Are Divisible by kLC 1497 · 24:00
    MediumGoogle · Amazon · +5 more companiesLeetCode ↗ (opens in a new tab)
  46. Longest Balanced Substring IILC 3714 · 42:48
    MediumGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)
  47. Maximum Unique Subarray Sum After DeletionLC 3487 · 9:41
    EasyGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)
  48. Smallest Missing Integer Greater Than Sequential Prefix SumLC 2996 · 10:27
    EasyGoogle · Amazon · +2 more companiesLeetCode ↗ (opens in a new tab)

  49. Grouping & Canonical Keys

    0 of 2 passed
  50. Word Pattern -(Amazon, MakeMyTrip, Microsoft) : Explanation ➕ Live CodingLC 290 · 28:34
    EasyGoogle · Amazon · +6 more companiesLeetCode ↗ (opens in a new tab)
  51. Isomorphic StringsLC 205 · 19:02
    EasyGoogle · Amazon · +13 more companiesLeetCode ↗ (opens in a new tab)

  52. Set Membership & Dedup

    0 of 5 passed
  53. Unique Number of OccurrencesLC 1207 · 12:19
    EasyGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)
  54. Replace WordsLC 648 · 14:34
    MediumGoogle · Microsoft · +2 more companiesLeetCode ↗ (opens in a new tab)
  55. Find the Number of Distinct Colors Among the BallsLC 3160 · 24:27
    MediumGoogle · Amazon · +1 more companiesLeetCode ↗ (opens in a new tab)
  56. Minimum Number of Operations to Make Elements in Array DistinctLC 3396 · 16:26
    EasyGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)
  57. Maximum Unique Subarray Sum After DeletionLC 3487 · 9:41
    EasyGoogle · Amazon · +3 more companiesLeetCode ↗ (opens in a new tab)

  58. Hash Design

    0 of 1 passed
  59. Smallest Number in Infinite SetLC 2336 · 31:08
    MediumGoogle · Amazon · +4 more companiesLeetCode ↗ (opens in a new tab)

All 48 stations in order

  1. 1.Find Players With Zero or One Losses (LeetCode 2225)
  2. 2.Unique Number of Occurrences (LeetCode 1207)
  3. 3.Word Pattern -(Amazon, MakeMyTrip, Microsoft) : Explanation ➕ Live Coding (LeetCode 290)
  4. 4.Smallest Number in Infinite Set (LeetCode 2336)
  5. 5.Equal Row and Column Pairs (LeetCode 2352)
  6. 6.Number of Good Pairs (LeetCode 1512)
  7. 7.Binary Trees With Factors (LeetCode 823)
  8. 8.Restore the Array From Adjacent Pairs (LeetCode 1743)
  9. 9.Count Nice Pairs in an Array (LeetCode 1814)
  10. 10.Array Pair Sum Divisibility Problem
  11. 11.Minimum Number of Pushes to Type Word I and II (LeetCode 3014)
  12. 12.Hand of Straights (LeetCode 846)
  13. 13.Replace Words (LeetCode 648)
  14. 14.Check If Array Pairs Are Divisible by k (LeetCode 1497)
  15. 15.Find the Number of Distinct Colors Among the Balls (LeetCode 3160)
  16. 16.Count Number of Bad Pairs (LeetCode 2364)
  17. 17.Minimum Index of a Valid Split (LeetCode 2780)
  18. 18.Rabbits in Forest (LeetCode 781)
  19. 19.Total Characters in String After Transformations I (LeetCode 3335)
  20. 20.Longest Palindrome by Concatenating Two Letter Words (LeetCode 2131)
  21. 21.Bitwise ORs of Subarrays (LeetCode 898)
  22. 22.Vowel Spellchecker (LeetCode 966)
  23. 23.Next Greater Numerically Balanced Number (LeetCode 2048)
  24. 24.Count Special Triplets (LeetCode 3583)
  25. 25.Count Covered Buildings (LeetCode 3531)
  26. 26.Maximum Square Area by Removing Fences From a Field (LeetCode 2975)
  27. 27.Minimum Pair Removal to Sort Array II (LeetCode 3510)
  28. 28.Longest Balanced Substring II (LeetCode 3714)
  29. 29.Check if Strings Can be Made Equal With Operations I and II (LeetCode 2839)
  30. 30.Minimum Distance Between Three Equal Elements I and II (LeetCode 3741)
  31. 31.Closest Equal Element Queries (LeetCode 3488)
  32. 32.Minimum Absolute Distance Between Mirror Pairs (LeetCode 3761)
  33. 33.Count the Number of Special Characters II (LeetCode 3121)
  34. 34.Find the Maximum Number of Elements in Subset (LeetCode 3020)
  35. 35.Evaluate the Bracket Pairs of a String (LeetCode 1807)
  36. 36.Destination City (LeetCode 1436)
  37. 37.Path Crossing (LeetCode 1496)
  38. 38.Redistribute Characters to Make All Strings Equal (LeetCode 1897)
  39. 39.Isomorphic Strings (LeetCode 205)
  40. 40.Count the Number of Consistent Strings (LeetCode 1684)
  41. 41.Minimum Number of Operations to Make Elements in Array Distinct (LeetCode 3396)
  42. 42.Minimum Operations to Make Array Values Equal to K (LeetCode 3375)
  43. 43.Number of Equivalent Domino Pairs (LeetCode 1128)
  44. 44.Find Lucky Integer in an Array (LeetCode 1394)
  45. 45.Maximum Unique Subarray Sum After Deletion (LeetCode 3487)
  46. 46.Coupon Code Validator (LeetCode 3606)
  47. 47.N-Repeated Element in Size 2N Array (LeetCode 961)
  48. 48.Smallest Missing Integer Greater Than Sequential Prefix Sum (LeetCode 2996)