最好的办法，以找出是否IEnumerable的＆LT;＆GT;具有独特的价值 [英] Best way to find out if IEnumerable<> has unique values

问题描述

我有很多的code中，我做这样的事情

I have a lot of code in which I do something like this

bool GetIsUnique(IEnumerable<T> values)
{
    return values.Count() == values.Distinct().Count;
}

有没有更好更快更好的方式来做到这一点？

Is there a better faster nicer way to do this?

推荐答案

您的方法需要通过序列重复两次，有一些潜在的缺点的：

Your method needs to iterate through the sequence twice, with a few of potential drawbacks:

1. 在迭代两次会比一次迭代任何显著规模的序列比较慢。
2. 在某些序列会如果您尝试迭代他们不止一次地抛出一个异常;其他人可能会有不同的结果后续的迭代。
3. 您的方法使用计数，需要在每次迭代整个序列。有没有理由你不应该打破，早早出局，只要你知道，有一个重复的值。

1. Iterating twice will be slower than iterating once for sequences of any significant size.
2. Some sequences will throw an exception if you try to iterate them more than once; others might return different results for subsequent iterations.
3. Your method uses Count which needs to iterate the entire sequence each time. There's no reason why you shouldn't break-out early as soon as you know that there's a duplicate value.

下面的方法只需要通过序列重复一次，将打破，早早出局，只要任何重复的值遇到：

The following method only needs to iterate through the sequence once, and will break-out early as soon as any duplicate value is encountered:

bool GetIsUnique<T>(IEnumerable<T> values)
{
    var set = new HashSet<T>();

    foreach (T item in values)
    {
        if (!set.Add(item))
            return false;
    }
    return true;
}

这篇关于最好的办法，以找出是否IEnumerable的＆LT;＆GT;具有独特的价值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！