1 Joe Meehean

 List of names  Set of names  Map names as keys phone #’s as values Phil Bill Will Phil Bill Will Phil Bill Will Phil: Bill: Will: [Phil, Will, Bill]

 Unordered collection of items without duplicates  List implementation add => O(N): check for uniqueness contains => O(N) bad idea  Balanced tree implementation much better (we’ll see more about this later)

 set  Key is the data type being stored  Compare is a comparator  Ignore Alloc (almost never needed)

 pair insert(const T &key) inserts the key bool is true if key not already in set  size_type erase(const T &key) removes the item from the set  iterator find(const T &key) returns iterator to key  iterator begin(), end()

 Both store collections of objects  Lists are ordered, sets are not items have a position in a list positions are meaningless in sets  Duplicates list can contain duplicates sets cannot

 Implementation lists: array or linked list sets are balanced trees or hash tables  Some operations are faster in a set remove contains  Use a set when… don’t have/want duplicates position does not matter need fast contains and remove

 An unordered collection of unique keys with associated values no duplicate keys allowed  Generalization of an array arrays can only be indexed by ordinal data types maps can be indexed with any comparable type  What is ordinal data types? type with 1-to-1 mapping integers

 Maps verb: a key is associated with stated value e.g., B maps to 2 symbol: B => 2  Mapping noun: key-value pair symbol: B => 2  Associative array, dictionary nouns: other words for map

 map  Key is the data type of the key  Data is the data type of the value  Compare is a comparison functor  Ignore Alloc (almost never needed)

 Map methods  Overloads the [ ] operator  Insert map[“Bill”] = 27  Access cout << map[“Bill”] << endl;  Erase map.erase(“Bill”)

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