Chapter 13
Standard Template Library (STL) II
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Chapter Objectives
• Learn more about the standard template
library (STL)
• Become familiar with the associative
containers
• Explore how associative containers are used
to manipulate data in a program
• Learn about various generic algorithms
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Class pair
The class pair has two constructors: the default constructor,
and a constructor with two parameters. The general syntax to
declare an object of the type pair is:
where expr1 is of the type Type1 and expr2 is of the
type Type2
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Relational Operators for the class
pair
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Type pair and
Function make_pair
The header file utility also contains the definition of the
function template make_pair.
With the help of the function make_pair, we can create
pairs without explicitly specifying the type pair.
template<class T1, class T2>
pair<T1, T2> make_pair(const T1& X, const T2& Y)
{
return (pair<T1, T2>(X, Y));
}
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Associative Containers in STL
• Elements in associative container automatically
sorted according to some ordering criteria
• Default ordering criterion is relational operator <
(less than)
• Users can also specify their own ordering criterion
• Predefined Associative Containers
–
–
–
–
Sets
Multisets
Maps
multimaps
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Various Ways to Declare a
Set/Multiset Container
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Various Ways to Declare a
Set/Multiset Container
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Operations in a set or multiset
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Associative Containers: map and
multimap
• Containers map and multimap manage their
elements in the form key/value
• Elements automatically sorted according to some
sort criteria applied on key
• Default sorting criterion is relational operator <
(less than)
• User can also specify other sorting criteria
• For user-defined data types, relational operators
must be properly overloaded
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Associative Containers: map and
multimap
• Only difference between containers map
and multimap is: container multimap allows
duplicates, whereas the container map does
not
• The name of the class defining the container
map is map; the name of the class defining
the container multimap is multimap
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Associative Containers: map and
multimap
• The name of the header file containing the
definitions of the classes map and multimap, and
the definitions of the functions to implement
various operations on these containers, is map
• Therefore, to use any of these containers, the
program must include the following statement:
#include <map>
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Various Ways to Declare a
map/multimap Container
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Various Ways to Declare a
map/multimap Container
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Operations in a map/multimap
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Containers, Header Files, and
Iterators
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Algorithms
• Some operations very specific to container;
provided as part of container definition
• Generic algorithms common to all
containers; contained in header file
algorithm:
– Find
– Sort
– Merge
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STL Algorithm Classification
• Nonmodifying algorithms
– Investigate, do not modify elements of
container
• Modifying algorithms
– Modify the elements of a container by
rearranging, removing, or changing the values
of the elements
– Mutating algorithms: change order f elements
but not their value
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STL Algorithm Classification
• Numeric algorithms
– Designed to perform numeric calculations on
elements
• Heap algorithms
– Implement heap sort
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Nonmodifying Algorithms
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Modifying Algorithms
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Numeric and Heap Algorithms
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Function Objects
• To make the generic algorithms flexible, the STL
usually provides two forms of an algorithm using
the mechanism of function overloading
• First form of algorithm uses natural operation to
accomplish this goal
• In second form, user can specify criteria based on
which the algorithm processes the elements
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Function Objects
• A function object contains a function that can be
treated as a function using the function call
operator, ()
• A function object is a class template that overloads
the function call operator, ()
• In addition to allowing you to create your own
function objects, STL provides arithmetic,
relational, and logical function objects
• STL’s function objects contained in header file
functional
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Arithmetic STL Function Objects
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Relational STL Function Objects
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Relational STL Function Objects
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Logical STL Function Objects
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Predicates
• Special types of function objects that return
boolean values
• Unary predicates check a specific property
for a single argument
• Binary predicates check a specific property
for a pair of (two) arguments
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Predicates
• Typically used to specify a searching or
sorting criterion
• In STL, always return the same result for
the same value
• The functions that modify their internal
states cannot be considered predicates
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Insert Iterators
• STL provides three insert iterators to insert
elements at destination
• Class vector does not support the
push_front operation, this iterator cannot be
used for a vector container
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Insert Iterators
• Back_inserter
– Uses the push_back operation of the container in place
of the assignment operator
• Front_inserter
– Uses the push_front operation of the container in place
of the assignment operator
• Inserter
– Uses the container’s insert operation in place of the
assignment operator
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Functions and Their Uses
• fill: used to fill a container with elements
• fill_n: used to fill in the next n elements
• generate and generate_n: used to generate
elements and fill a sequence
• find, find_if, find_end, and find_first_of:
used to find the elements in a given range
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Functions and Their Uses
• remove: used to remove certain elements
from a sequence
• remove_if: used to remove certain elements
from a sequence using some criterion
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Functions and Their Uses
• remove_copy: copies the elements in a
sequence into another sequence by
excluding certain elements from the first
sequence
• remove_copy_if: copies the elements in a
sequence into another sequence by
excluding certain elements, using some
criterion, from the first sequence
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Functions and Their Uses
• swap, iter_swap, and swap_ranges: used to
swap elements
• search, search_n, sort, and binary_search:
used to search elements
• adjacent_find: used to find the first
occurrence of consecutive elements
satisfying a certain criterion
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Algorithms
• merge: merges two sorted lists
• inplace_merge: used to combine two sorted,
consecutive sequences
• reverse: reverses the order of the elements in a
given range
• reverse_copy: reverses the order of the elements in
a given range while copying into a destination
range.The source is not modified
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Algorithms
• rotate: rotates the elements in a given range
• rotate_copy: copies the elements of the
source at the destination in a rotated order
• count: counts the occurrences of a specified
value in a given range
• count_if: counts the occurrences of a
specified value in a given range satisfying a
certain criterion
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Algorithms
• max: used to determine the maximum of
two values
• max_element: is used to determine the
largest element in a given range
• min: used to determine the minimum of two
values
• min_element: used to determine the
smallest element in a given range
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Algorithms
• random_shuffle: used to randomly order the
elements in a given range
• for_each: used to access and process each
element in a given range by applying a
function, which is passed as a parameter
• transform: creates a sequence of elements
by applying certain operations to each
element in a given range
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Algorithms
• includes: determines whether the elements of one
range appear in another range
• set_intersection: used to find the elements that are
common to two ranges of elements
• set_union: used to find the elements that are
contained in two ranges of elements
• set_difference: used to find the elements in one
range of elements that do not appear in another
range of elements
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Algorithms
• set_symmetric_difference: given two ranges
of elements, determines elements in first
range but not the second, or in second range
but not first
• accumulate, adjacent_difference,
inner_product, and partial_sum: numerical
functions that manipulate numeric data
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Chapter Summary
•
•
•
•
Standard Template Library (STL)
Associative Containers
Operations on associative containers
Function and algorithms on associative
containers
• Example usage of function and algorithms
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