patrick
3b98d704d1
Went with Lagrange interpolation instead because that seemed easier. Co-authored-by: Smaug123 <patrick+github@patrickstevens.co.uk> Reviewed-on: #10
56 lines
1.4 KiB
Forth
56 lines
1.4 KiB
Forth
namespace AdventOfCode2023
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open System
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[<RequireQualifiedAccess>]
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module Day9 =
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let extrapolate (isStart : bool) (arr : ResizeArray<int64>) =
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let mutable answer = 0L
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let pos = if isStart then -1L else int64 arr.Count
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for i = 0 to arr.Count - 1 do
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let mutable product = Rational.ofInt arr.[i]
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for j = 0 to arr.Count - 1 do
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if j <> i then
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product <- product * Rational.make (pos - int64 j) (int64 i - int64 j)
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answer <- answer + Rational.assertIntegral product
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answer
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let part1 (s : string) =
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use s = StringSplitEnumerator.make '\n' s
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let mutable answer = 0L
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let arr = ResizeArray ()
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for line in s do
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arr.Clear ()
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use line = StringSplitEnumerator.make' ' ' line
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for number in line do
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let number = Int64.Parse number
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arr.Add number
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answer <- answer + extrapolate false arr
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answer
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let part2 (s : string) =
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use s = StringSplitEnumerator.make '\n' s
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let mutable answer = 0L
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let arr = ResizeArray ()
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for line in s do
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arr.Clear ()
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use line = StringSplitEnumerator.make' ' ' line
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for number in line do
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let number = Int64.Parse number
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arr.Add number
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answer <- answer + extrapolate true arr
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answer
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