更新:我的问题已经解决,我更新了我的问题中的代码源以与Jason的答案匹配。请注意,rikitikitik的答案是解决从带替换的样本中选择卡片的问题。
我想从加权列表中选择x个随机元素。采样是不重复的。我找到了这个回答:https://dev59.com/D3I95IYBdhLWcg3wzhd9#2149533,其中包含Python的实现。我在C#中实现并测试了它。但结果(如下所述)与我预期的不符。我对Python一无所知,因此我确定我在将代码移植到C#时犯了错误,但我看不出来,因为Python中的代码非常好文档化。
我选择了一张卡片10000次,这是我获得的结果(结果在执行中保持一致):
我想从加权列表中选择x个随机元素。采样是不重复的。我找到了这个回答:https://dev59.com/D3I95IYBdhLWcg3wzhd9#2149533,其中包含Python的实现。我在C#中实现并测试了它。但结果(如下所述)与我预期的不符。我对Python一无所知,因此我确定我在将代码移植到C#时犯了错误,但我看不出来,因为Python中的代码非常好文档化。
我选择了一张卡片10000次,这是我获得的结果(结果在执行中保持一致):
Card 1: 18.25 % (10.00 % expected)
Card 2: 26.85 % (30.00 % expected)
Card 3: 46.22 % (50.00 % expected)
Card 4: 8.68 % (10.00 % expected)
您可以看到,卡片1和卡片4的权重都为1,但是无论我选2张还是3张卡片,卡片1总是比卡片4被选中的次数多得多。
测试数据:
var cards = new List<Card>
{
new Card { Id = 1, AttributionRate = 1 }, // 10 %
new Card { Id = 2, AttributionRate = 3 }, // 30 %
new Card { Id = 3, AttributionRate = 5 }, // 50 %
new Card { Id = 4, AttributionRate = 1 }, // 10 %
};
这是我的C#实现:
public class CardAttributor : ICardsAttributor
{
private static Random random = new Random();
private List<Node> GenerateHeap(List<Card> cards)
{
List<Node> nodes = new List<Node>();
nodes.Add(null);
foreach (Card card in cards)
{
nodes.Add(new Node(card.AttributionRate, card, card.AttributionRate));
}
for (int i = nodes.Count - 1; i > 1; i--)
{
nodes[i>>1].TotalWeight += nodes[i].TotalWeight;
}
return nodes;
}
private Card PopFromHeap(List<Node> heap)
{
Card card = null;
int gas = random.Next(heap[1].TotalWeight);
int i = 1;
while (gas >= heap[i].Weight)
{
gas -= heap[i].Weight;
i <<= 1;
if (gas >= heap[i].TotalWeight)
{
gas -= heap[i].TotalWeight;
i += 1;
}
}
int weight = heap[i].Weight;
card = heap[i].Value;
heap[i].Weight = 0;
while (i > 0)
{
heap[i].TotalWeight -= weight;
i >>= 1;
}
return card;
}
public List<Card> PickMultipleCards(List<Card> cards, int cardsToPickCount)
{
List<Card> pickedCards = new List<Card>();
List<Node> heap = GenerateHeap(cards);
for (int i = 0; i < cardsToPickCount; i++)
{
pickedCards.Add(PopFromHeap(heap));
}
return pickedCards;
}
}
class Node
{
public int Weight { get; set; }
public Card Value { get; set; }
public int TotalWeight { get; set; }
public Node(int weight, Card value, int totalWeight)
{
Weight = weight;
Value = value;
TotalWeight = totalWeight;
}
}
public class Card
{
public int Id { get; set; }
public int AttributionRate { get; set; }
}