Map Data Type (9.2)

















What's a Map?


	1. a data structure that associates keys with values
	2. a set of key-value pairs
	3. keys are unique, values can be repeated



What are some examples of Maps?


	phone book (name -> number)

	dictionary (word -> definition)

















What operations are supported by a Map?
What's the abstract interface for a Map?


	size();
	add(key, value);
	remove(key);
	getValue(key);

















Maps in the C++ Library


	#include <map>

	std::map

















What are some of the operations supported by std::map?


	size_t size() const;
	size_t count ( const KeyType& key ) const;
	size_t erase ( const KeyType& key ); // returns number of items erased
	ValueType& operator[] ( const KeyType& key ); // key is added
					              // if not already in map


How do you add a new mapping?

	map["bob"] = 16;


How do you remove a mapping?

	map.erase("bob");

















How do you iterate over a map?


	iterator points to a pair object
	pair->first is the key
	pair->second is the value



DEMO	(demo6, iterate over a map)



DEMO	(demo8, word frequency counter)