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Shifting blocks of elements…Model of a list object…Sample listThe list ADTCLASS list ConstructorsCLASS list Operations (7 slides)CLASS list::iterator OperationsInserting an element into a listRemoving an element from a listOrdered listsSplicing two listsSummary Slides (5 slides)

Chapter 6 Chapter 6 – – The List Container and IteratorsThe List Container and Iterators

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Shifting blocks of elements to Shifting blocks of elements to insert or delete a vector iteminsert or delete a vector item

15 20 30 35 40Initial V ec to r

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Model of a list object with links Model of a list object with links to next and previous elementto next and previous element

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Sample listSample list

Pasta Delectica

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The List ADTThe List ADT The list API documents the member function

prototype as well as pre- and postconditions.– provides three constructors to declare a list object.

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CLASS list Constructors <list>

list();Create an empty list. This is the default constructor.

list(int n, const T&value = T());Create a list with n elements, each having a specified value. If the value argument is omitted, the elements

are filled with the default value for type T. Type T must have a default constructor, and the default value of type T is specified by the notation T().

list(T *first, T *last);Initialize the list, using the address range [first, last).

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CLASS list Operations <list>

T& back();Return the value of the item at the rear of the list. Precondition: The vector must contain at least one

element.

bool empty() const;Return true if the vector is empty, false otherwise.

T& front();Return the value of the item at the front of the list. Precondition: The vector must contain at least one

element.

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CLASS list Operations <list>

void push_back(const T& value);Add a value at the rear of the list. Postcondition: The list has a new element at the

rear, and its size increases by 1.

void pop_back();Remove the item at the rear of the list. Precondition: The list is not empty. Postcondition: The list has a new element at the rear

or is empty.

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CLASS list Operations <list>

void push_front(const T& value);Add a value at the front of the list. Postcondition: The list has a new element at the

front, and its size increases by 1.

void pop_front();Remove the item at the front of the list. Precondition: The list is not empty. Postcondition: The list has a new element at the front

or is empty.

int size() const;Return the number of elements in the vector.

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CLASS list Operations <list>

iterator begin();Returns an iterator that references the first position

(front) of the list. If the list is empty, the iterator value end() is returned.

const_iterator begin();Returns a const_iterator that points to the first position (front) of a constant list. If the list is empty, the

const_iterator value end() is returned.

iterator end();Returns an iterator that signifies a location immediately out of the range of actual elements. A program must

not dereference the value of end() with the * operator.

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CLASS list Operations <list>

iterator end();Returns an iterator that signifies a location immediately out of the range of actual elements. A program must

not dereference the value of end() with the * operator.

const_iterator end();Returns a const_iterator that signifies a location

immediately out of the range of actual elements in a constant list. A program must not dereference the value of end() with the * operator.

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CLASS list Operations <list>

void erase(iterator pos);Erase the element pointed to by pos.Precondition: The list is not empty.Postcondition: The list has one fewer element.

void erase(iterator first, iterator last);Erase all list elements within the iterator range [first,

last].Precondition: The list is not empty.Postcondition: The size of the list decreases by the

number of elements in the range.

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CLASS list Operations <list>

iterator insert(iterator pos, const T& value);Insert value before pos, and return an iterator pointing to the position of the new value in the list. The

operation does not affect any existing iterators.Postcondition: The list has a new element.

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CLASS list::iterator Operations <list>

*:Accesses the value of the item currently pointed to by the iterator.

*iter;*iter;

++: Moves the iterator to the next item in the list. iter++;iter++;

--: Moves the iterator to the previous item in the list.

iter--;iter--;

==: Takes two iterators as operands and returns truewhen they both point at the same item in the list.

iter1 == iter2iter1 == iter2

!=: Returns true when the two iterators do not point at the same item in the list.

iter1 != iter2iter1 != iter2

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Inserting an element into a listInserting an element into a list

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Removing an element from a listRemoving an element from a list

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Ordered listsOrdered lists8 27 46 0

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Position the iterator curr at the front of the list.

Insert 50 in the list:

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Splicing two listsSplicing two lists

7 1 5 1 6 3 47 1 5 3 47 3 4

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1 5 1 6

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Summary Slide 1Summary Slide 1

§- list - A Sequence of elements stored by position.

- Index access is not available…§- to access the value of an element, must pass

through its preceding elements.

§- list iterator- A generalized pointer that moves through a list

element by element… forward or backward

- At any point, the * operator accesses the value of a list item.

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Summary Slide 2Summary Slide 2

§- The list class has two iterator types:1)1) iteratoriterator:

A generalized list traversal pointer.

2)2) constconst __ iteratoriterator:

must be used with a constant list object. Each type is a nested class of list and must be

accessed by using the scope operator ::::

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Summary Slide 3Summary Slide 3

§- the list member function begin()- Gives an iterator an initial value that points to the

first element.

§- the list member function end()- Returns an iterator pointing just past the last

element of the list.

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Summary Slide 4Summary Slide 4

§- The sequential search of a list object- implemented by using an iterator range

[firstfirst, lastlast).

- It returns an iterator that points at the target value or has value lastlast if the target is not in the list.

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Summary Slide 5Summary Slide 5

§- list class member fns insert() and erase()

- Both use an iterator argument to modify a list.

1)1) insert()insert(): places value in the list before the data

referenced by the iterator pospos.

2)2) erase()erase():removes the data item referenced by pospos from the list.