英文:
Get top n values including duplicates with LINQ
问题
以下是翻译好的部分：
请考虑这个列表：
城市 值
---------------------
城市1 10
城市2 20
城市3 30
城市4 40
城市5 50
城市6 60
如果我想要获取前3个城市中的最高值，我可以编写以下的LINQ查询：
MyList.OrderByDescending(o=>o.Value).Take(3);
现在考虑这个列表：
城市 值
---------------------
城市1 10
城市2 20
城市3 30
城市4 40
城市5 50
城市6 60
城市7 60
我想要一个查询，返回所有具有前3个最高值的城市。对于上述列表，我想要以下结果：
城市 值
---------------------
城市7 60
城市6 60
城市5 50
城市4 40
谢谢。
英文:
Please consider this list:
City Value
---------------------
City1 10
City2 20
City3 30
City4 40
City5 50
City6 60
If I want to get top 3 Values in Cities I can write this LINQ:
MyList.OrderByDescending(o=>o.Value).Take(3);
Now consider this list:
City Value
---------------------
City1 10
City2 20
City3 30
City4 40
City5 50
City6 60
City7 60
I want a query that return all cities with top 3 highest values. For above list I want this result:
City Value
---------------------
City7 60
City6 60
City5 50
City4 40
Thanks
答案1
得分: 14
This list will contain all cities with the top 3 highest values, sorted in descending order by value.
英文:
var result = MyList.GroupBy(o => o.Value)
.OrderByDescending(g => g.Key)
.Take(3)
.SelectMany(g => g)
.ToList();
This list will contain all cities with the top 3 highest values, sorted in descending order by value.
答案2
得分: 0
A bit clunky, this solution finds the third highest DISTINCT value, then returns all values equal or greater to it.
using System.Diagnostics.CodeAnalysis;
var MyList = new List<(string, string)>();
MyList.Add(("City1", "10"));
MyList.Add(("City2", "20"));
MyList.Add(("City3", "30"));
MyList.Add(("City4", "40"));
MyList.Add(("City5", "50"));
MyList.Add(("City6", "60"));
MyList.Add(("City7", "60"));
var topThreeDistinct = MyList.Distinct(new StringStringComparer()).OrderByDescending(o => o.Item2).Take(3).ToList();
var thirdValue = topThreeDistinct[2].Item2;
Console.WriteLine($"Third value = {thirdValue}");
var topThreeAll = MyList.Where(o => o.Item2.CompareTo(thirdValue) >= 0 ).ToList();
foreach (var item in topThreeAll)
Console.WriteLine(item);
Console.WriteLine("FINISHED");
class StringStringComparer : IEqualityComparer<(string, string)>
{
public bool Equals((string, string) x, (string, string) y)
{
if (x.Item2 == y.Item2)
{
return true;
}
else
{
return false;
};
}
public int GetHashCode([DisallowNull] (string, string) obj)
{
return Convert.ToInt32(obj.Item2);
}
}
(C# .NET 6.0 Console App)
英文:
A bit clunky, this solution finds the third highest DISTINCT value, then returns all values equal or greater to it.
using System.Diagnostics.CodeAnalysis;
var MyList = new List<(string, string)>();
MyList.Add(("City1", "10"));
MyList.Add(("City2", "20"));
MyList.Add(("City3", "30"));
MyList.Add(("City4", "40"));
MyList.Add(("City5", "50"));
MyList.Add(("City6", "60"));
MyList.Add(("City7", "60"));
var topThreeDistinct = MyList.Distinct(new StringStringComparer()).OrderByDescending(o => o.Item2).Take(3).ToList();
var thirdValue = topThreeDistinct[2].Item2;
Console.WriteLine($"Third value = {thirdValue}");
var topThreeAll = MyList.Where(o => o.Item2.CompareTo(thirdValue) >= 0 ).ToList();
foreach (var item in topThreeAll)
Console.WriteLine(item);
Console.WriteLine("FINISHED");
class StringStringComparer : IEqualityComparer<(string, string)>
{
public bool Equals((string, string) x, (string, string) y)
{
if (x.Item2 == y.Item2)
{
return true;
}
else
{
return false;
};
}
public int GetHashCode([DisallowNull] (string, string) obj)
{
return Convert.ToInt32(obj.Item2);
}
}
(C# .NET 6.0 Console App)
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