使用Walker的Alias方法进行加权随机选择

我在找这个算法
（将从每个元素具有不同被挑选概率（权重）的元素列表中随机选择的算法）
并且发现只有python和c实现，在我做了一个C＃之后，有点不同（但我认为更简单）我想我应该分享它，我也需要一个F＃imlementation ，如果有人可以做到它请发表回答

using System; using System.Collections.Generic; using System.Linq; namespace ChuckNorris { class Program { static void Main(string[] args) { var oo = new Dictionary { {"A",7}, {"B",1}, {"C",9}, {"D",8}, {"E",11}, }; var rnd = new Random(); var pick = rnd.Next(oo.Values.Sum()); var sum = 0; var res = ""; foreach (var o in oo) { sum += o.Value; if(sum >= pick) { res = o.Key; break; } } Console.WriteLine("result is "+ res); } } } 

如果有人可以用F＃重拍它，请发布你的代码

Answer 1

这是F＃中的类似代码：

 let rng = new System.Random() let d = [| "A", 3 "B", 2 "C", 3 |] let sums = Seq.scan (+) 0 (dict d).Values |> Seq.skip 1 |> Seq.toArray let pick = rng.Next(sums.[sums.Length-1]) let res = fst d.[sums |> Seq.findIndex ((<) pick)] 

Answer 2

 open System let oo = dict [ "A", 7; "B", 1; "C", 9; "D", 8; "E", 11 ] let rnd = Random() let pick = oo.Values |> Seq.sum |> rnd.Next let res = oo |> Seq.scan (fun (_, s) (KeyValue(k, v)) -> k, s + v) ("", 0) |> Seq.tryPick (fun (k, s) -> if s >= pick then printfn "Result is %s" k; Some k else None)