如何获取LINQ以返回集合中具有最大值的对象的索引? [英] How can I get LINQ to return the index of the object which has the max value in a collection?
问题描述
我有一个不可变对象的列表(在我的特定情况下是Tuple<double, double>
的列表),我想更改具有最高Item2值的对象.
I have a list of immutable objects (in my specific case a list of Tuple<double, double>
) and I'd like to change the one with the highest Item2 value.
理想情况下,我可以使用IndexOfMaxBy函数,所以我可以这样做:
Ideally there would be an IndexOfMaxBy function I could use, so I could do:
var indexOfPointWithHighestItem2 = myList.IndexOfMaxBy(x => x.Item2);
var original = myList[indexOfPointWithHighestItem2];
myList[indexOfPointWithHighestItem2] =
new Tuple<double, double>(original.Item1, original.Item2 - 1);
我看过乔恩·斯基特(Jon Skeet)的MaxBy函数与Select结合使用,我可以做到:
I have seen How can I get LINQ to return the object which has the max value for a given property?, and using Jon Skeet's MaxBy function combined with Select I could do:
var indexOfPointWithHighestItem2 =
myList.Select((x, i) => new { Index = i, Value = x })
.MaxBy(x => x.Item2).Index;
但这会为列表中的每个对象创建一个新对象,并且必须有一种更整洁的方法.有人有什么好的建议吗?
But this creates a new object for every object in my list, and there must be a neater way. Does anyone have any good suggestions?
推荐答案
如果愿意,您当然可以自己编写IndexOfMaxBy
扩展名.
Well, if you wanted to, you could of course write an IndexOfMaxBy
extension yourself.
示例(未经测试):
public static int IndexOfMaxBy<TSource, TProjected>
(this IEnumerable<TSource> source,
Func<TSource, TProjected> selector,
IComparer<TProjected> comparer = null
)
{
//null-checks here
using (var erator = source.GetEnumerator())
{
if (!erator.MoveNext())
throw new InvalidOperationException("Sequence is empty.");
if (comparer == null)
comparer = Comparer<TProjected>.Default;
int index = 0, maxIndex = 0;
var maxProjection = selector(erator.Current);
while (erator.MoveNext())
{
index++;
var projectedItem = selector(erator.Current);
if (comparer.Compare(projectedItem, maxProjection) > 0)
{
maxIndex = index;
maxProjection = projectedItem;
}
}
return maxIndex;
}
}
用法:
var indexOfPointWithHighestItem2 = myList.IndexOfMaxBy(x => x.Item2);
这篇关于如何获取LINQ以返回集合中具有最大值的对象的索引?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!