1. Vectors, lists and queues
STL Data Types in C++
Vectors, lists and queues

2. The Standard Template Library
As we have already seen C++ supports all of the data types and structures that C offers.
As well as these there is the data types in the standard template library.
These are held in a separate library from C++ and are available for many (if not most) C++ implmentations.

3. #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{ vector <string> v;
cout << " Enter lines of text to be sorted,\n";
cout << " followed by the word stop:\n";
for (;;)
{string s;
getline(cin,s);
if ( s == "stop")
break;
v.push_back(s);
} //for
sort(v.begin(), v.end());
cout << " The samelines after sorting: \n";
for (int i=0; i < v.size(); i++)
cout << v[i] << endl;
return 0; }

4. Vectors Note the use of #includes vector <string> v declaration
v.push_back(s) method call
sort(v.begin(), v.end()) call to sort function
With vector methods as parameters
cout << v[i] << endl; access to vector elements

5. Using iterators
In the STL there are a special class of access types, called iterators, that act as pointers to the special classes like vectors.
These are declared with the cumbersome syntax
vector <string>::iterator i
Obviously the above is for our vector of strings.

6. #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{ vector <string> v;
cout << " Enter lines of text to be sorted,\n";
cout << " followed by the word stop:\n";
for (;;)
{string s;
getline(cin,s);
if ( s == "stop")
break;
v.push_back(s);
} //for
sort(v.begin(), v.end());
cout << " The samelines after sorting: \n";
for (vector <string>::iterator i=v.begin(); i != v.end(); i++)
cout << *i << endl;
return 0; }

7. Reverse iterators
It is possible to go backwards through a vector using a reverse iterator
This is declared
vector <string>::reverse_iterator i;
It would be used as follows
For (i=v.rbegin(); i != v.rend(); i++)
cout << *i << endl;
This would go backward through the vector – despite the ++ operation!

8. Vectors, Lists and Deques
The above are known as container adaptors. They all offer efficient means of storage and retrieval.
The simplest change to our program would have been to use a deque instead of a vector.
The following program shows how slight, in syntax that program is.

9. #include <iostream>
#include <string>
#include <deque>
#include <algorithm>
using namespace std;
int main()
{ deque <string> v;
cout << " Enter lines of text to be sorted,\n";
cout << " followed by the word stop:\n";
for (;;)
{string s;
getline(cin,s);
if ( s == "stop")
break;
v.push_back(s);
} //for
sort(v.begin(), v.end());
cout << " The samelines after sorting: \n";
for (deque <string>::iterator i=v.begin(); i != v.end(); i++)
cout << *i << endl;
return 0; }

10. Vectors, lists and deques
Vectors permit data to be added/deleted at the end of the vector. Can randomly access data.
Deques permit data to be added/deleted at the beginning or end. Can randomly access data.
List can add or delete data at any position in the list. Can’t randomly access data.

11. Vectors, lists and deques
vector <type>
Insert &
Delete here
deque <type>
Insert &
Delete here
list <type>
Insert &
Delete at
Any position

12. Example list program #include <string> #include <iostream>
#include <list>
using namespace std;
void showlist (const string &str, const list<int> &L)
{ list<int>::const_iterator i;
cout << str << endl << " ";
for (i=L.begin(); i != L.end(); i++)
cout << *i << " ";
cout << endl; }

13. int main()
{ list<int> L; int x;
cout <<"Enter positive integers, followed by 0: \n";
while (cin >> x, x != 0 )
L.push_back(x);
showlist("Initial list:", L);
L.push_front(123);
showlist("After inserting 123 at beginning: ", L);
list<int>::iterator i = L.begin();
L.insert(++i,456);
showlist("After inserting 456 at the second position: ", L);
i = L.end();
L.insert(--i,999);
showlist("After inserting 999 just before the end: ", L);
i = L.begin(); x = *i;
L.pop_front();
cout << "Deleted at the beginning: " << x << endl;
showlist("After this deletion: ", L);
i = L.end(); x = *--i;
L.pop_back();
cout << "Deleted at the end: " << x << endl;
i = L.begin();
x = *++i; cout << "To be deleted: " << x << endl;
L.erase(i);
showlist("After this deletion (of second element): ", L);
return 0; }

15. Points to note with list
The use of
void showlist (const string &str, const list<int> &L)
list<int>::const_iterator i;
The member functions
push_front(), push_back(), insert() and erase()
The latter 2 being random access functions
Also note the use of
i = L.end(); x = *--i;