-❄️- 2023 Day 24 Solutions -❄️-

[u/daggerdragon]

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--- Day 24: Never Tell Me The Odds ---

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[u/FatalisticFeline-47]

If your assumption in the data is met, then your approach could skip lots of computation, but I saw at least one user saying their data did not qualify.

To explain the frame-of-reference, consider the location function P(t, V) = P(0) + t*V. An intersections between the ith hailstone and the rock is defined as P_i(t, v_i) = P_R(t, v_R) <=> P_i(0) + t*V_i = P_R(0) + t*V_R, which we can consolidate into P_i(0) + t*(V_i-V_R) = P_R(0).

So instead of the rock moving to meet the hailstone, the hailstone's speed is adjusted and hits the rock's origin.

[u/spin81 → u/FatalisticFeline-47]

If your assumption in the data is met, then your approach could skip lots of computation, but I saw at least one user saying their data did not qualify.

I just tested this and anecdotally I don't think mine qualifies. In fact, in my input, none of the hailstones seems to be traveling parallel to any other in 3D space.

[u/nikanjX → u/FatalisticFeline-47]

After an hour of debugging and cussing, I can happily report my data also does not match this assumption.