从具有加权元素的数组中获取随机元素 [英] Get random element from array with weighted elements

问题描述

我有一组对象代表我正在尝试开发的游戏中的生物.这些对象(除其他外)具有唯一标识符和生成权重(或概率).

I have an array of objects that represent creatures in a game I'm trying to develop. These objects have (among others) a unique identifier and a weight (or probability) to spawn.

我正在尝试开发一种算法来随机生成生物，但我没有想出一种使用权重的方法(我真的不知道该怎么做).

I'm trying to develop an algorithm to spawn creatures randomly but I fail to come up with a way to use the weights (I really don't know how to do it).

有人可以帮忙吗?

生物数组的一个例子可能是:

An example of creatures array could be:

var creatures = [
    {id: 1, weight: 25},
    {id: 2, weight: 15},
    {id: 3, weight: 5},
    {id: 4, weight: 45},
    {id: 5, weight: 10}
]

推荐答案

我在这个 博客 我认为适合您的需求.

I found this nice algorithm implemented in PHP in this blog that I think migth suit your needs.

我刚刚将它采用给 JS.

I just adopted it to JS.

var creatures = [{
    id: 1,
    weight: 25
  }, {
    id: 2,
    weight: 15
  }, {
    id: 3,
    weight: 5
  }, {
    id: 4,
    weight: 45
  }, {
    id: 5,
    weight: 10
  }],
  sumOfWeights = creatures.reduce(function(memo, creature) {
    return memo + creature.weight;
  }, 0),
  selectedWeigths = {};

function getRandom(sumOfWeights) {
  var random = Math.floor(Math.random() * (sumOfWeights + 1));

  return function(creature) {
    random -= creature.weight;
    return random <= 0;
  };
}

for (var i = 0; i < 1000; i++) {
  var creature = creatures.find(getRandom(sumOfWeights));
  selectedWeigths[creature.weight] = (selectedWeigths[creature.weight] || 0) + 1;
}

console.log(selectedWeigths);

希望有帮助.

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