常用算法帖(C#): 集合
集合类型的数据结构在日常编程中占重要比例，大多数的业务需求都需要用到集合类型的数据结构。.NET平台为我们提供了种类繁多的集合类型的数据结构，我们只需要简单的调用相应的API就能完成对零散数据的整理。本文收集了目前.NET平台下为我们提供的所有集合类型，并提供一个小例子。
IEnumerablenamespace System.Collections.Generic{ public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); }}public static void EnumerableTest() { List<string> tmp = new List<string>(); tmp.Add("Apple"); tmp.Add("Grape"); tmp.Add("Watermelon"); strEnumerable = tmp as IEnumerable<string>; if (tmp != null) { var iterator=strEnumerable.GetEnumerator(); while (iterator.MoveNext()) { Console.WriteLine(iterator.Current); } } /*OUTPUT Apple Grape Watermelon */ }ICollection
namespace System.Collections.Generic{ public interface ICollection<T> : IEnumerable<T>, IEnumerable { bool IsReadOnly { get; } void Clear(); void CopyTo(T[] array, int arrayIndex); bool Remove(T item); }}public static void CollectionTest() { List<int> sourceTable=new List<int>(); sourceTable.Add(69); sourceTable.Add(57); sourceTable.Add(87); intCollection = sourceTable as ICollection<int>; if (intCollection != null) { Console.WriteLine("Current collection has {0} elements totally", intCollection.Count); var iterator = intCollection.GetEnumerator(); while (iterator.MoveNext()) { Console.WriteLine(iterator.Current); } } /*OUT PUT Current collection has 3 elements totally 69 57 87 */ }
namespace System.Collections.Generic{ public interface IList<T> : ICollection<T>, IEnumerable<T>, IEnumerable { T this[int index] { get; set; } void Insert(int index, T item); void RemoveAt(int index); }}public static void ListTest() { List<float> temperatureTable = new List<float>(); temperatureTable.Add(1.20f); temperatureTable.Add(5.43f); temperatureTable.Add(8.64f); floatList = temperatureTable as IList<float>; if (floatList != null) { Console.WriteLine("Current collection has {0} elements totally", floatList.Count); var iterator = floatList.GetEnumerator(); while (iterator.MoveNext()) { Console.WriteLine(iterator.Current); } } /*OUT PUT Current collection has 3 elements totally 1.2 5.43 8.64 */ }
namespace System.Collections.Generic{ public interface ISet<T> : ICollection<T>, IEnumerable<T>, IEnumerable { bool Add(T item); void ExceptWith(IEnumerable<T> other); void IntersectWith(IEnumerable<T> other); bool IsProperSubsetOf(IEnumerable<T> other); bool IsProperSupersetOf(IEnumerable<T> other); bool IsSubsetOf(IEnumerable<T> other); bool IsSupersetOf(IEnumerable<T> other); bool Overlaps(IEnumerable<T> other); bool SetEquals(IEnumerable<T> other); void SymmetricExceptWith(IEnumerable<T> other); void UnionWith(IEnumerable<T> other); }}public static void SetTest() { ////无序集合HashSet HashSet<string> charaterList = new HashSet<string>(); charaterList.Add("A"); charaterList.Add("B"); charaterList.Add("C"); if (!charaterList.Add("A")) { Console.WriteLine("Current Collection already have the 'A'"); } foreach (string tmp in charaterList) { Console.WriteLine(tmp); } Console.WriteLine(); /*OUTPUT Current Collection already have the 'A' A B C */ ////有序集合SortedSet SortedSet<string> charaterList2 = new SortedSet<string>(); charaterList2.Add("A"); charaterList2.Add("B"); charaterList2.Add("D"); charaterList2.Add("C"); charaterList2.Add("G"); charaterList2.Add("E"); charaterList2.Add("F"); if (!charaterList2.Add("A")) { Console.WriteLine("Current Collection already have the 'A'"); } foreach (string tmp in charaterList2) { Console.WriteLine(tmp); } /*OUT PUT * Current Collection already have the 'A' A B C D E F G */ ////IsSubSetOf()和IsSuperSetOf()方法 //int[] onetoten = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; //int[] fivetoeight = new int[] { 5, 6, 7, 8 }; HashSet<int> onetoten = new HashSet<int>(); onetoten.Add(1); onetoten.Add(2); onetoten.Add(3); onetoten.Add(4); onetoten.Add(5); onetoten.Add(6); onetoten.Add(7); onetoten.Add(8); onetoten.Add(9); onetoten.Add(10); HashSet<int> fivetoeight = new HashSet<int>(); fivetoeight.Add(5); fivetoeight.Add(6); fivetoeight.Add(7); fivetoeight.Add(8); HashSet<int> eleventofifteen = new HashSet<int>(); eleventofifteen.Add(11); eleventofifteen.Add(12); eleventofifteen.Add(13); eleventofifteen.Add(14); eleventofifteen.Add(15); eleventofifteen.Add(1); if (fivetoeight.IsSubsetOf(onetoten)) { Console.WriteLine("fivetoeight is subset of onetoten."); } if (fivetoeight.IsSupersetOf(fivetoeight)) { Console.WriteLine("ontoten is superset of fivetoten"); } /* OUT PUT fivetoeight is subset of onetoten. ontoten is superset of fivetoten */ onetoten.UnionWith(eleventofifteen);//这里包含重复的元素 Console.WriteLine("unio"); foreach (int tmp in onetoten) { Console.WriteLine(tmp); } onetoten.IntersectWith(fivetoeight); Console.WriteLine("intersect"); foreach (int tmp in onetoten) { Console.WriteLine(tmp); } Console.WriteLine("except"); onetoten.ExceptWith(fivetoeight); foreach (int tmp in onetoten) { Console.WriteLine(tmp); } /*OUT PUT: first execute the union operation, * second execute the intersection operation using last result, * third execute the exception operation using last result. * unio 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 intersect 5 6 7 8 except * * */ }
namespace System.Collections.Generic{ public interface IDictionary<TKey, TValue> : ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable { ICollection<TKey> Keys { get; } ICollection<TValue> Values { get; } TValue this[TKey key] { get; set; } void Add(TKey key, TValue value); bool ContainsKey(TKey key); bool Remove(TKey key); bool TryGetValue(TKey key, out TValue value); }} public static void DictionaryTest() { Dictionary<string, string> programBook = new Dictionary<string, string>(); programBook.Add("chapter1", "base programming skill"); programBook.Add("chapter2", "the amateurism programming skill"); programBook.Add("chapter3", "the professional programming skill"); programBook.Add("chapter4", "the god programming skill"); strDictionary = programBook as IDictionary<string, string>; if (strDictionary != null) { Random rand = new Random(); string[] content = strDictionary.Keys.ToArray<string>(); Console.WriteLine(strDictionary[content[rand.Next(0, 4)]]); } /**OUT PUT base programming skill * **/ }
namespace System.Linq{ public interface ILookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>, IEnumerable { int Count { get; } IEnumerable<TElement> this[TKey key] { get; } bool Contains(TKey key); }}public static void LookupTest() { Person[] persons = new Person[]{ new Person{firstName="Li",lastName="Ming",age=21}, new Person{firstName="Li",lastName="XinLiang",age=22}, new Person{firstName="Wang",lastName="Kai",age=23}, new Person{firstName="Li",lastName="SiMing",age=24} }; var personsContent = persons.ToLookup(person => person.firstName); ILookup<string, Person> ok = persons.ToLookup<Person, string>(a => a.firstName); foreach (Person tmp in personsContent["Li"]) { Console.WriteLine(tmp.firstName + tmp.lastName); } Console.WriteLine("*"); foreach (Person tmp in ok["Li"]) { Console.WriteLine(tmp.firstName + tmp.lastName); } /*OUT PUT LiMing LiXinLiang LiSiMing * LiMing LiXinLiang LiSiMing */ }
namespace System.Collections.Generic{ public interface IComparer<in T> { int Compare(T x, T y); }} public static void IComparerTest() { List<Person> people = new List<Person>(); Person jim = new Person { firstName = "jim", lastName = "wang", age = 30 }; Person bank = new Person { firstName = "bank", lastName = "Li", age = 90 }; Person Lily = new Person { firstName = "Lily", lastName = "Qin", age = 38 }; people.Add(bank); people.Add(Lily); people.Add(jim); Person tmp = new Person(); IComparer<Person> compararion = tmp as IComparer<Person>; people.Sort(compararion); foreach (Person p in people) { Console.WriteLine(p.firstName); } /*OUT PUT jim Lily bank */ }
用法见《常用算法帖(C#): 数组 》
namespace System.Collections.Generic{ public interface IEqualityComparer<in T> { bool Equals(T x, T y); int GetHashCode(T obj); }}IGrouping
namespace System.Linq{ public interface IGrouping<out TKey, out TElement> : IEnumerable<TElement>, IEnumerable { TKey Key { get; } }} public static void IGroupingTest() { Person[] persons = new Person[]{ new Person{firstName="Li",lastName="Ming",age=21}, new Person{firstName="Li",lastName="XinLiang",age=22}, new Person{firstName="Wang",lastName="Kai",age=23}, new Person{firstName="Li",lastName="SiMing",age=24} }; ILookup<string, Person> ok = persons.ToLookup<Person, string>(a => a.firstName); var iterator = ok.GetEnumerator(); while (iterator.MoveNext()) { Console.WriteLine(iterator.Current.Key); } }
public static void ObserverCollectionTest() { ObservableCollection<string> paperFirm = new ObservableCollection<string>(); string[] personList = new string[] { "Bank", "Bruce" }; paperFirm.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(paperFirm_CollectionChanged); paperFirm.Add("Jim"); paperFirm.Add("Lucy"); paperFirm.Add("Alex"); paperFirm.Add("Jeff"); paperFirm.Remove("Jim");//删除jim paperFirm.Remove("Lucy");//删除lucy paperFirm.Clear();//这个事件会触发 Reset事件 /*OUT PUT you add a element in 0,it is value is Jim you add a element in 1,it is value is Lucy you add a element in 2,it is value is Alex you add a element in 3,it is value is Jeff you remove a element in 0,it is value is Jim you remove a element in 0,it is value is Lucy reset event! */ } static void paperFirm_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { if (e.Action == NotifyCollectionChangedAction.Add) { Console.WriteLine(string.Format("you add a element in {0},it is value is {1}", new object[] { e.NewStartingIndex, ((ObservableCollection<string>)sender)[e.NewStartingIndex] })); } if (e.Action == NotifyCollectionChangedAction.Remove) { Console.WriteLine(string.Format("you remove a element in {0},it is value is {1}", new object[] { e.OldStartingIndex, e.OldItems[0] })); } if (e.Action == NotifyCollectionChangedAction.Replace) { } if (e.Action == NotifyCollectionChangedAction.Reset) { Console.WriteLine("reset event!"); } }