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Datastrukturer og Collections

Datastrukturer og Collections. Oversigt og forskel imellem Jave og . net Collections library Collection interfaces ArrayList IList interface Hashtable Hashtable traversering. Oversigt og forskel imellem J ave og .net. Abstrakte datatyper: lister/sekvenser stak kø

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Datastrukturer og Collections

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  1. Datastrukturer og Collections • Oversigt og forskel imellem Jave og .net • Collections library • Collection interfaces • ArrayList • IListinterface • Hashtable • Hashtabletraversering Rasmus D. Lehrmann

  2. Oversigt og forskel imellem Jave og .net • Abstrakte datatyper: • lister/sekvenser • stak • kø • Table/Map/Dictionary • Java-specifik: • Collections (generics) • Collection • Set • List • Map • .NET-specifik: • Collections.Generics • IDictionary • IList • Algoritmer: • søgning • sweep • sortering • del&hersk • rekursion • Datastrukturer: • statisk/dynamisk • array • kædet liste • træer: • søgetræer • balancerede • hashing Rasmus D. Lehrmann

  3. Collections library • Datastruktureri .NET kaldesnormaltCollections • Klasser: • Array • ArrayList • Hashtable • Stack • Queue Rasmus D. Lehrmann

  4. Collection interfaces • Collections implementer forskellige interfaces for at sikreensartethed • Klasserder implementer samme interface tilbydersamme services • gørbiblioteketlettere at læreogbruge • gørmuligt at skrivegenerisk code op mod interfacet • Interfaces: • ICollection • IEnumerable • IEnumerator • IList • IComparer • IComparable Rasmus D. Lehrmann

  5. ArrayList • ArrayList opbevare sekvenser af elementer • dataen er gemt i et array, der automatisk ændrer størrelse • bliver primært manipuleret via Ilist public class ArrayList : IList, IEnumerable, ... { // IList services ... // additional services int Capacity { get... set... } void TrimToSize() intBinarySearch(object value) intIndexOf (object value, intstartIndex) intLastIndexOf (object value, intstartIndex) ... } control of memory in underlying array searching Rasmus D. Lehrmann

  6. IList interface • IListdefinerersekvenserafelementer • kantilgås via index public interface IList : ICollection { int Add (object value); void Insert(int index, object value); void Remove (object value); void RemoveAt(int index); void Clear (); bool Contains(object value); intIndexOf (object value); object this[int index] { get; set; } boolIsReadOnly { get; } boolIsFixedSize { get; } } add new elements remove containment testing read/write existing element (see comment) structural properties Rasmus D. Lehrmann

  7. Hashtable • Hashtableunderstøtter collections af key/value pairs • keys skalværeunikke, values indeholder data • gemmerobject reference tilbåde key og value • GetHashCodemetodeaf key brugestil at bestemmeplacering Hashtable ages = new Hashtable(); ages["Ann"] = 27; ages["Bob"] = 32; ages.Add("Tom", 15); ages["Ann"] = 28; int a = (int) ages["Ann"]; create add update retrieve Rasmus D. Lehrmann

  8. Hashtabletraversering • TraverseringafHashtableindhold • hvert element er en DictionaryEntrystruktur • data gemmesiKeyogValue properties Hashtable ages = new Hashtable(); ages["Ann"] = 27; ages["Bob"] = 32; ages["Tom"] = 15; foreach (DictionaryEntry entry in ages) { string name = (string) entry.Key; int age = (int) entry.Value; ... } enumerate entries get key and value Rasmus D. Lehrmann

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