类型实现《程序员的第一年》--------------C#中System.Collections.Generic.SortedDictionary 的使用
在改章节中,我们主要介绍类型实现的内容,自我感觉有个不错的建议和大家分享下
SortedDictionary<TKey,TValue>
类型参数
TKey
字典中的键的类型。
TValue
字典中的值的类型。
SortedDictionary 泛型类是索检算运复杂度为 O(log n) 的二叉搜索树，其中 n 是字典中的元素数。就这一点而言，
它与 SortedList 泛型类相似。这两个类拥有相似的对象模型，并且都拥有 O(log n) 的索检算运复杂度。这两个类的
别区在于内存的应用以及入插和移除元素的速度：
SortedList 应用的内存比 SortedDictionary 少。
SortedDictionary 可对未排序的据数执行更快的入插和移除作操：它的时间复杂度为 O(log n)，而 SortedList 为 O
(n)。
如果应用排序据数一次性填充列表，则 SortedList 比 SortedDictionary 快。
个每键/值对都可以作为 KeyValuePair 构结行进索检，或作为 DictionaryEntry 通过非泛型 IDictionary 接口行进检
索。
只要键用作 SortedDictionary 中的键，它们就必须是不可变的。SortedDictionary 中的个每键必须是一唯的。键不能
为 空引用（在 Visual Basic 中为 Nothing），但是如果值类型 TValue 为引用类型，该值则可认为空。
SortedDictionary 须要比拟器实现来执行键比拟。可以应用一个接受 comparer 参数的构造函数来指定 IComparer 泛
型接口的实现；如果不指定实现，则应用认默的泛型比拟器 Comparer.Default。如果类型 TKey 实现
System.IComparable 泛型接口，则认默比拟器应用该实现。
C# 言语的 foreach 语句，须要集合中个每元素的类型。由于 SortedDictionary 的个每元素都是一个键/值对，因此元
素类型既不是键的类型，也不是值的类型。而是 KeyValuePair 类型。上面的码代演示 C# 法语
using System;
using System.Collections.Generic;
public class Example
{
public static void Main()
{
// Create a new dictionary of strings, with string keys.
//
Dictionary<string, string> openWith =
new Dictionary<string, string>();
// Add some elements to the dictionary. There are no
// duplicate keys, but some of the values are duplicates.
openWith.Add("txt", "notepad.exe");
openWith.Add("bmp", "paint.exe");
openWith.Add("dib", "paint.exe");
openWith.Add("rtf", "wordpad.exe");
// The Add method throws an exception if the new key is
// already in the dictionary.
try
{
openWith.Add("txt", "winword.exe");
}
catch (ArgumentException)
{
Console.WriteLine("An element with Key = \"txt\" already exists.");
}
// The Item property is another name for the indexer, so you
// can omit its name when accessing elements.
Console.WriteLine("For key = \"rtf\", value = {0}.",
openWith["rtf"]);
// The indexer can be used to change the value associated
// with a key.
openWith["rtf"] = "winword.exe";
Console.WriteLine("For key = \"rtf\", value = {0}.",
openWith["rtf"]);
// If a key does not exist, setting the indexer for that key
// adds a new key/value pair.
openWith["doc"] = "winword.exe";
// The indexer throws an exception if the requested key is
// not in the dictionary.
try
{
Console.WriteLine("For key = \"tif\", value = {0}.",
openWith["tif"]);
}
catch (KeyNotFoundException)
{
Console.WriteLine("Key = \"tif\" is not found.");
}
// When a program often has to try keys that turn out not to
// be in the dictionary, TryGetValue can be a more efficient
// way to retrieve values.
string value = "";
if (openWith.TryGetValue("tif", out value))
{
Console.WriteLine("For key = \"tif\", value = {0}.", value);
}
else
{
Console.WriteLine("Key = \"tif\" is not found.");
}
// ContainsKey can be used to test keys before inserting
// them.
if (!openWith.ContainsKey("ht"))
{
openWith.Add("ht", "hypertrm.exe");
Console.WriteLine("Value added for key = \"ht\": {0}",
openWith["ht"]);
}
// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
Console.WriteLine();
foreach( KeyValuePair<string, string> kvp in openWith )
{
Console.WriteLine("Key = {0}, Value = {1}",
kvp.Key, kvp.Value);
}
// To get the values alone, use the Values property.
Dictionary<string, string>.ValueCollection valueColl =
openWith.Values;
// The elements of the ValueCollection are strongly typed
// with the type that was specified for dictionary values.
Console.WriteLine();
foreach( string s in valueColl )
{
Console.WriteLine("Value = {0}", s);
}
// To get the keys alone, use the Keys property.
Dictionary<string, string>.KeyCollection keyColl =
openWith.Keys;
// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
Console.WriteLine();
foreach( string s in keyColl )
{
Console.WriteLine("Key = {0}", s);
}
// Use the Remove method to remove a key/value pair.
Console.WriteLine("\nRemove(\"doc\")");
openWith.Remove("doc");
if (!openWith.ContainsKey("doc"))
{
Console.WriteLine("Key \"doc\" is not found.");
}
}
}
* This code example produces the following output:
An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe
Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe
Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht
Remove("doc")
Key "doc" is not found.
*/
文章结束给大家分享下程序员的一些笑话语录： 程序员的愿望
有一天一个程序员见到了上帝.上帝: 小伙子,我可以满足你一个愿望.程序员: 我希望中国国家队能再次打进世界杯.
上帝: 这个啊!这个不好办啊,你还说下一个吧!
程序员: 那好!我的下一个愿望是每天都能休息6个小时以上.
上帝: 还是让中国国家打进世界杯.
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