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4Sum

advancedlayer B4 · Two pointers5 tests

Given an integer array nums and an integer target, return every unique quadruplet [a, b, c, d] drawn from four distinct positions whose sum equals target.

  • Two quadruplets are the same if they hold the same multiset of values — report each only once
  • The order of the quadruplets, and the order inside each one, does not matter
  • Return [] when none exist
  • Target complexity: O(n^3). Beware of the four-nested-loop trap

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