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Python dictionary and set exercises

Counting, grouping and looking things up with dictionaries and sets, in problems checked by tests in your browser.

Start with Count the Votes

Beginner

  1. 28. Count the VotesThe polls have closed: time to count every ballot30 XP5 min
  2. 42. First One of a KindIn a crowd of repeats, who showed up only once?40 XP8 min
  3. 252. Merge Two Contact ListsTwo address books, one tidy list with nobody in it twice40 XP8 min

Intermediate

  1. 64. Repeats Close TogetherHas anything come back too soon?60 XP10 min
  2. 77. Two SumSomewhere in the list, two numbers make the target65 XP10 min
  3. 91. Group the AnagramsSame letters, different words: sort them into families75 XP12 min
  4. 102. The K Most FrequentWhich values keep turning up more than any others?80 XP14 min

Advanced

  1. 117. Pairs That Differ by KHow many different pairs sit exactly k apart?110 XP18 min
  2. 136. Longest Consecutive RunHidden in the jumble: the longest unbroken count125 XP20 min
  3. 151. Subarrays That Sum to KHow many stretches of the list add up to exactly k?135 XP22 min
  4. 162. Smallest Rectangle From PointsFour of these dots make a box. How small can it be?150 XP28 min

Expert

  1. 171. Zero Sum Across Four ListsOne number from each of four lists: how often do they cancel out?190 XP25 min
  2. 184. Lamps on a Huge GridLamps light rows, columns and diagonals. Is this square in the dark?230 XP40 min
  3. 188. Most Points on One LineLay a ruler across the dots: how many can it touch at once?240 XP45 min

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