使用 Walker 的别名方法进行加权随机选择 [英] Weighted random selection using Walker's Alias Method
本文介绍了使用 Walker 的别名方法进行加权随机选择的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我在找这个算法
(算法将从元素列表中随机选择每个元素具有不同的被选中概率(权重))
并且只找到了 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,我还需要一个 F# 实现,如果有人能做到的话请发布答案
I was looking for this algorithm
(algorithm which will randomly select from a list of elements where each element has different probability of being picked (weight) )
and found only python and c implementations, after I did a C# one, a bit different (but I think simpler) I thought I should share it, also I need an F# imlementation, if anyone can make it please post an answer
using System;
using System.Collections.Generic;
using System.Linq;
namespace ChuckNorris
{
class Program
{
static void Main(string[] args)
{
var oo = new Dictionary<string, int>
{
{"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);
}
}
}
如果有人可以在 F# 中重新制作它,请发布您的代码
推荐答案
以下是 F# 中的类似代码:
Here is the similar code in F#:
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)]
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