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Two pointers problems in Python

Walk a sequence from both ends or at two speeds: the two-pointer technique, on problems with tests.

Start with Move Zeros to the End

Beginner

  1. 38. Move Zeros to the EndSweep every zero to the back of the line35 XP6 min
  2. 44. Merge Two Sorted ListsZip two sorted lines of numbers into one40 XP8 min
  3. 244. Squares of a Sorted ListSquaring turns the negatives around: can you keep the list in order?35 XP8 min

Intermediate

  1. 62. Pair Sum in a Sorted ListTwo prices that use up the budget exactly60 XP10 min
  2. 112. Container With the Most WaterPick the two walls that hold the most water90 XP18 min
  3. 269. Fewest LifeboatsTwo people per boat and a weight limit: how many boats does the ferry need?60 XP12 min
  4. 292. Three-Colour SortA jumble of three kinds of tokens, put in order in a single sweep65 XP12 min

Advanced

  1. 123. Overlapping Free TimesTwo busy calendars: when are both people free?115 XP20 min
  2. 145. Count Possible TrianglesHow many triangles hide in a bag of sticks?135 XP25 min
  3. 164. Three Numbers That Sum to ZeroEvery trio of numbers that cancels out150 XP30 min
  4. 362. Three Numbers Closest to a TargetPick three numbers whose total lands as close to the target as possible125 XP25 min

Expert

  1. 182. Trapping Rain WaterAfter the storm, how much rain sits between the bars?220 XP40 min

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