124 lines
3.4 KiB
Forth
124 lines
3.4 KiB
Forth
namespace AdventOfCode2023
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open System
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[<RequireQualifiedAccess>]
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module Day13 =
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let rowToInt (row : ReadOnlySpan<char>) : uint32 =
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let mutable mult = 1ul
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let mutable answer = 0ul
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for c = row.Length - 1 downto 0 do
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if row.[c] = '#' then
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answer <- answer + mult
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mult <- mult * 2ul
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answer
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let colToInt (grid : ReadOnlySpan<char>) (rowLength : int) (colNum : int) =
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let mutable mult = 1ul
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let mutable answer = 0ul
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for i = grid.Count '\n' - 1 downto 0 do
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if grid.[i * (rowLength + 1) + colNum] = '#' then
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answer <- answer + mult
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mult <- mult * 2ul
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answer
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let verifyHorizontalReflection (group : ResizeArray<'a>) (smaller : int) (bigger : int) : bool =
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let midPoint = (smaller + bigger) / 2
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let rec isOkWithin (curr : int) =
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if smaller + curr > midPoint then
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true
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else if group.[smaller + curr] = group.[bigger - curr] then
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isOkWithin (curr + 1)
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else
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false
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if not (isOkWithin 0) then
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false
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else
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smaller = 0 || bigger = group.Count - 1
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/// Find reflection among rows
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[<TailCall>]
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let rec findRow (rows : ResizeArray<'a>) (currentLine : int) =
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if currentLine = rows.Count - 1 then
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None
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else
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let mutable answer = UInt32.MaxValue
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let mutable i = currentLine
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while i < rows.Count - 1 do
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i <- i + 1
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if currentLine % 2 <> i % 2 then
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if rows.[i] = rows.[currentLine] then
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if verifyHorizontalReflection rows currentLine i then
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answer <- uint32 (((currentLine + i) / 2) + 1)
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i <- Int32.MaxValue
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if answer < UInt32.MaxValue then
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Some answer
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else
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findRow rows (currentLine + 1)
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let part1 (s : string) =
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let mutable s = s.AsSpan ()
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use lines = StringSplitEnumerator.make' '\n' s
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let rows = ResizeArray ()
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let cols = ResizeArray ()
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let mutable answer = 0ul
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while not s.IsEmpty do
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rows.Clear ()
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cols.Clear ()
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let index = s.IndexOf "\n\n"
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let group =
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if index < 0 then
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// last group
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s
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else
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s.Slice (0, index + 1)
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let lineLength = s.IndexOf '\n'
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cols.EnsureCapacity lineLength |> ignore
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for col = 0 to lineLength - 1 do
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cols.Add (colToInt group lineLength col)
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for row in StringSplitEnumerator.make' '\n' group do
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if not row.IsEmpty then
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rows.Add (rowToInt row)
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match findRow rows 0 with
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| Some rowIndex -> answer <- answer + 100ul * rowIndex
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| None ->
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let colIndex = Option.get (findRow cols 0)
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answer <- answer + colIndex
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if index < 0 then
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s <- ReadOnlySpan<char>.Empty
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else
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s <- s.Slice (index + 2)
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answer
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let part2 (s : string) =
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use mutable lines = StringSplitEnumerator.make '\n' s
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let mutable answer = 0uL
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for line in lines do
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if not line.IsEmpty then
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()
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answer
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