1 / 10

Map and Multimap

Map and Multimap. ITK 169 Fall 2003. Map. A Standard Templated Library #include <map> Each value of a map is a pair. The pair is made up of a key and an element. The key may be of any type and it is what determines the ordering of the map.

lilka
Télécharger la présentation

Map and Multimap

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Map and Multimap ITK 169 Fall 2003

  2. Map • A Standard Templated Library • #include <map> • Each value of a map is a pair. • The pair is made up of a key and an element. • The key may be of any type and it is what determines the ordering of the map. • The element is the type of “things” stored in the map.

  3. The key • In program 5, the key was a data member of the Player object and the object was never actually stored in the map. • map<string, int> playerIndex; • Here, we did not have a map of Players – rather we had a map of indexes. • The integer stored as the second element of the pair was the record number or location of this player in the file. • This is one way a map could be used.

  4. Program 6 • In program 6 we might have decided to store our collection of Person pointers in a map instead of a list. map<string name, Person*> mymap; • Here name would have been a complete name – last first – not stored individually as in the actual object. • This would have automatically sorted the collection by name.

  5. map Elements are Unique • In a map, the key must be a unique element. • Therefore if you have a map of students and you make their grade point the key, each student’s grade point would have to be unique (which is not likely to happen).

  6. miltimap • A multimap is a map that allows elements with duplicate keys. • Still - #include <map>

  7. map Methods • As with the other STL classes, the expected methods are available: • Constructors • size • empty • insert • erase • find • begin • end

  8. pairs • The insert method takes a value that is a pair as its argument • A pair is defined pair<keyType, elementType> name(first, second); • So if we have a map defined as: map<string, double> students; • And we have a pair defined as: pair<string, double> aStu(“Smith, Bob”, 3.96); • We could insert the pairs using: students.insert(aStu);

  9. Associative Array • In typical arrays, the index is always an integer. • In associative arrays, the index can be any type – int, double, string, or some user defined object • An assignment like students[“Brown, Mary”] = 3.5; • Inserts the pair <“Brown, Mary”, 3.5> into the students map.

  10. Using Dynamic Help

More Related