adventOfCode/challenges/2021/05-hydrothermalVenture

Day 5: Hydrothermal Venture

Part one

• Parse input and output a list of pairs of points.
• Remove diagonal lines by filtering the list using the condition that p1.x == p2.x or p1.y == p2.y
• Count overlapping points
  • Create a dictionary that uses the point coordinate as a key and contains an integer n for each key
  • Iterate over each line in the input, adding 1 to n for each coordinate in the line
    • The coordinates were founid by computing the x and y deltas between the two points that made up the line
    • The sign of the deltas determines the direction we step in
    • We then step through each point in the line based on the step directions until the final point is encountered
  • Iterate over all keys in the dictionary and count every point where n > 1

Part two

The same as part one, but without the list filtering step.

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Involved literal napkin maths.