Geometry Basics

  • Orientation via cross product
  • Line sweep for overlaps
  • Closest pair in O(n log n)
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Orientation

  • cross = (B-A) x (C-A)
  • sign tells turn direction
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Line sweep

  • Convert to events
  • Sort, sweep, maintain active count
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Closest pair

  • Divide and conquer
  • Check strip neighbors by y
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