问题描述
检查字典中的重复值并打印其键的最快方法是什么?
What can be the fastest way to to check the duplicate values in the dictionary and print its key?
字典 MyDict 具有以下值，
关键价值
22 100
24 200
25 100
26 300
29 200
39 400
41 500
示例:键 22 和 25 具有相同的值，我需要打印 22 和 25 具有重复值.
Example: key 22 and 25 have same values and i need to print that 22 and 25 have duplicate values.
推荐答案
视情况而定.如果您有一本不断变化的字典，并且只需要获取一次该信息，请使用:
It depends. If you have an ever changing dictionary and need to get that information only once, use this:
MyDict.GroupBy(x => x.Value).Where(x => x.Count() > 1)
但是，如果您的字典或多或少是静态的，并且需要多次获取此信息，则不应只将数据保存在字典中，还应将数据保存在 ILookup 中字典的值作为键，字典的键作为值:
However, if you have a dictionary that is more or less static and need to get this information more than once, you should not just save your data in a Dictionary but also in a ILookup with the value of the dictionary as the key and the key of the dictionary as the value:
var lookup = MyDict.ToLookup(x => x.Value, x => x.Key).Where(x => x.Count() > 1);
要打印信息，您可以使用以下代码:
To print the info, you can use the following code:
foreach(var item in lookup)
{
var keys = item.Aggregate("", (s, v) => s+", "+v);
var message = "The following keys have the value " + item.Key + ":" + keys;
Console.WriteLine(message);
}
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