solution for day 19

1 files changed, 15 insertions, 0 deletions

diff --git a/day19.fsx b/day19.fsx
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+open System
+
+let rec josephus = 
+    function
+        | 1 -> 1
+        | x  -> (if x % 2 <> 0 then 1 else -1) + 2 * josephus (x / 2)
+
+let josephus' (target: int): int =
+    let pow = Math.Pow(3, Math.Floor(Math.Log(target, 3))) |> int
+    if pow = target then pow
+    else if pow >= target / 2 then target - pow
+    else pow + (2 * (target - 2 * pow))
+
+josephus 3017957 |> printfn "%d"
+josephus' 3017957  |> printfn "%d"
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