More on the STL

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More on the STL

• vectorltTgt
• listltTgt
• stackltTgt
• queueltTgt
• priority_queueltTgt

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STL Container Classes

• Sequence containers organize items by position
  1st, 2nd, 3rd, ., last
• vector, list, deque
• Adapter containers are restricted versions of
  other containers
• stack, queue, priority_queue
• Associative containers organize items based on a
  key value
• set, map, multiset, multimap

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vectorltTgt vs. listltTgt

• vectorltTgt
• can expand to hold as many items as needed
• O(1) insert/delete at end of the list
• O(n) insert/delete at position i in the list
• indexing (veci) gives gives O(1) access to any
  position

• listltTgt
• can expand to hold as many items as needed
• O(1) delete of any item
• O(1) insert before any item
• no indexing cannot access item at position i in
  O(1)

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Use different storage structures
vectorltTgt items stored in an array (contiguous
storage)
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listltTgt items stored in a linked list
(non-contiguous storage)
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Partial listltTgt API

• list() //construct an
  empty list
• push_back(item) //add item at end of list
• pop_back() //remove item at end of
  list
• push_front(item) //add item at front of list
• pop_front() //remove item at front of
  list
• size() //return number of
  items in list
• back() //return item at end
  of list
• front() //return item at
  front of list

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STL iterators

• an iterator is a generalization of a pointer
• used to access an element in the container
• each STL container class has a nested iterator
  class associated with it
• vectorltTgtiterator
• listltTgtiterator
• STL container classes have methods which return
  iterators
• begin() //returns an iterator accessing first
  element
• end() //returns an iterator that is past
  the last //element

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iterator operations

• iter //access next element
• iter-- //access prior element
  
• and ! //compare 2 iterators
• iter //dereference the iterator

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An Example
listltintgt myList // store some items in
myList listltintgtiterator iter iter
myList.begin() while (iter ! myList.end())
//process iter iter
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STL Components

• Container classes - templates for classes which
  hold a collection of elements
• Algorithms - templates for functions which
  operate on a range of elements from a container
• range is specified by iterators
• Iterators
• give access to the element in a container
• allow for movement from one element to another

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STL Algorithms

• designed to operate on a sequence of elements
  rather than on a specific container
• the sequence is designated by two iterators
• all container classes have the following two
  methods
• begin( ) - returns an iterator positioned
  at the container's
  first element
• end( ) - returns an iterator
  positioned past the
  container's last element (past-the-end)
• C.begin( ), C.end( ) specifies a sequence which
  contains all elements of the container C

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STL Algorithms

• some examples of STL algorithms
• find(iter1, iter2, value) //returns an
  iterator
• max_element(iter1, iter2) //returns an iterator
• sort(iter1, iter2) //sorts
  using lt
• for_each(iter1, iter2, F) //applies F to
  every
  //item
• see STL Programmer's Guide link on home page

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include ltiostreamgt include ltvectorgt include
ltalgorithmgt include ltcstdlibgt using namespace
std void set(int val) void display(int val)
int main( ) vectorltintgt A(5)
for_each(A.begin( ), A.end( ), set) // would
not work if vectorltintgt A used
for_each(A.begin( ), A.end( ), display) cout
ltlt endl sort(A.begin( ), A.end( )) //
operatorlt must be defined for A's element type
for_each(A.begin( ), A.end( ), display) cout
ltlt endl return 0 void set(int val)
val rand( ) void display(int val) cout
ltlt " " ltlt val