Containers Library in STL gives us the Containers, which in simplest words, can be described as the objects used to contain data or rather collection of object. Containers help us to implement and replicate simple and complex data structures very easily like arrays, list, trees, associative arrays and many more.
The containers are implemented as generic class templates, means that a container can be used to hold different kind of objects and they are dynamic in nature!
Following are some common containers :
- vector : replicates arrays
- queue : replicates queues
- stack : replicates stack
- priority_queue : replicates heaps
- list : replicates linked list
- set : replicates trees
- map : associative arrays
Containers are classified into four categories :
Sequence containers : Used to implement data structures that are sequential in nature like arrays(array) and linked list(list).
Below is an example of implementing linked list, first by using structures and then by list containers.
#include <iostream>
struct node
{
int data;
struct node * next;
}
int main ()
{
struct node *list1 = NULL;
}
The above program is only creating a list node, no insertion and deletion functions are defined, to do that, you will have to write more line of code.
Now lets see how using Container Library simplifies it. When we use list containers to implement linked list we just have to include the list header file and use list constructor to initialize the list.
#include <iostream>
#include <list>
int main ()
{
list<int> list1;
}
And that's it! we have a list, and not just that, the containers library also give all the different methods which can be used to perform different operations on list such as insertion, deletion, traversal etc.
Thus you can see that it is incredibly easy to implement data structures by using Container library.
NOTE: Although Pair and Tuple are not actually the part of container library but we'll still discuss them as they are very commonly required in programming competitions and they make certain things very easy to implement.
pair<T1,T2> pair1, pair2 ;
The above code creates two pairs, namely pair1 and pair2, both having first object of type T1 and second object of type T2.
Now T1 will be referred as first and T2 will be referred as second member of pair1 and pair2.
Here are some function for pair template :
#include <iostream>
using namespace std;
int main ()
{
pair<int,int> pair1, pair3; //creats pair of integers
pair<int,string> pair2; // creates pair of an integer an a string
pair1 = make_pair(1, 2); // insert 1 and 2 to the pair1
pair2 = make_pair(1, "Studytonight") // insert 1 and "Studytonight" in pair2
pair3 = make_pair(2, 4)
cout<< pair1.first << endl; // prints 1, 1 being 1st element of pair1
cout<< pair2.second << endl; // prints Studytonight
if(pair1 == pair3)
cout<< "Pairs are equal" << endl;
else
cout<< "Pairs are not equal" << endl;
return 0;
}
Site Link : https://www.studytonight.com/cpp/stl/stl-pair-template
#include <iostream>
using namespace std;
template <class T>
class Calculator
{
private:
T num1, num2;
public:
Calculator(T n1, T n2)
{
num1 = n1;
num2 = n2;
}
void displayResult()
{
cout << "Numbers are: " << num1 << " and " << num2 << "." << endl;
cout << "Addition is: " << add() << endl;
cout << "Subtraction is: " << subtract() << endl;
cout << "Product is: " << multiply() << endl;
cout << "Division is: " << divide() << endl;
}
T add() { return num1 + num2; }
T subtract() { return num1 - num2; }
T multiply() { return num1 * num2; }
T divide() { return num1 / num2; }
};
int main()
{
Calculator<int> intCalc(2, 1);
Calculator<float> floatCalc(2.4, 1.2);
cout << "Int results:" << endl;
intCalc.displayResult();
cout << endl << "Float results:" << endl;
floatCalc.displayResult();
return 0;
}
/*
Container library is collection of classes
The container are implemented as genric classes
*/
#include<iostream>
#include<list>
using namespace std;
int main()
{
list<int> list1;
return 0;
}
Templates are powerful features of C++ which allows you to write generic programs. In simple terms, you can create a single function or a class to work with different data types using templates. Templates are often used in larger codebase for the purpose of code reusability and flexibility of the programs. The concept of templates can be used in two different ways: Function Templates Class Templates
Stl stand for standard template library this method tell which the value you are using from template Containters are used to manage collections of object of a certain kind vector can be used for creating dynamic array Function Templates A function template works in a similar to a normal function, with one key difference. A single function template can work with different data types at once but, a single normal function can only work with one set of data types. Normally, if you need to perform identical operations on two or more types of data, you use function overloading to create two functions with the required function declaration. However, a better approach would be to use function templates because you can perform the same task writing less and maintainable code. How to declare a function template? A function template starts with the keyword template followed by template parameter/s inside < > which is followed by function declaration.
template <class T>
T someFunction(T arg)
{
... .. ...
}
In the above code, T is a template argument that accepts different data types (int, float), and class is a keyword. You can also use keyword typename instead of class in the above example. When, an argument of a data type is passed to someFunction( ), compiler generates a new version of someFunction() for the given data type.
#include<iostream>
using namespace std;
template <class Temp>
Temp Large(Temp n1,Temp n2)
{
return (n1>n2)?n1:n2;
}
int main()
{
int i1,i2;
float f1,f2;
char c1,c2;
cout<<"Enter the two integer : \n";
cin>>i1>>i2;
cout<<Large(i1,i2)<<" is largest\n";
cout<<"Enter two floating point number : \n";
cin>>f1>>f2;
cout<<Large(f1,f2)<<" is largest\n";
cout<<"Enter two character : \n";
cin>>c1>>c2;
cout<<Large(c1,c2)<<" is largest\n";
return 0;
}
Templates are powerful features of C++ which allows you to write generic programs. In simple terms, you can create a single function or a class to work with different data types using templates. Templates are often used in larger codebase for the purpose of code reusability and flexibility of the programs. The concept of templates can be used in two different ways: Function Templates
Stl stand for standard template library this method tell which the value you are using from template Containters are used to manage collections of object of a certain kind vector can be used for creating dynamic array Function Templates A function template works in a similar to a normal function, with one key difference. A single function template can work with different data types at once but, a single normal function can only work with one set of data types. Normally, if you need to perform identical operations on two or more types of data, you use function overloading to create two functions with the required function declaration. However, a better approach would be to use function templates because you can perform the same task writing less and maintainable code. How to declare a function template? A function template starts with the keyword template followed by template parameter/s inside < > which is followed by function declaration.
template <class T>
T someFunction(T arg)
{
... .. ...
}
In the above code, T is a template argument that accepts different data types (int, float), and class is a keyword. You can also use keyword typename instead of class in the above example. When, an argument of a data type is passed to someFunction( ), compiler generates a new version of someFunction() for the given data type.
#include<iostream>
using namespace std;
template <class Temp>
Temp Large(Temp n1,Temp n2)
{
return (n1>n2)?n1:n2;
}
int main()
{
int i1,i2;
float f1,f2;
char c1,c2;
cout<<"Enter the two integer : \n";
cin>>i1>>i2;
cout<<Large(i1,i2)<<" is largest\n";
cout<<"Enter two floating point number : \n";
cin>>f1>>f2;
cout<<Large(f1,f2)<<" is largest\n";
cout<<"Enter two character : \n";
cin>>c1>>c2;
cout<<Large(c1,c2)<<" is largest\n";
return 0;
}
#include<iostream>
using namespace std;
template <typename T>
void Swap(T &n1,T &n2)
{
T temp;
temp=n1;
n1=n2;
n2=temp;
}
int main()
{
int i1=1,i2=2;
float f1=1.1,f2=2.2;
char c1='a',c2='b';
cout << "Before passing data to function template.\n";
cout << "i1 = " << i1 << "\ni2 = " << i2;
cout << "\nf1 = " << f1 << "\nf2 = " << f2;
cout << "\nc1 = " << c1 << "\nc2 = " << c2;
Swap(i1, i2);
Swap(f1, f2);
Swap(c1, c2);
cout << "\n\nAfter passing data to function template.\n";
cout << "i1 = " << i1 << "\ni2 = " << i2;
cout << "\nf1 = " << f1 << "\nf2 = " << f2;
cout << "\nc1 = " << c1 << "\nc2 = " << c2;
return 0;
}
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> vec;
int i;
cout<<"Vecotr size : "<<vec.size()<<"\n";
for(i=0;i<5;i++)
{
vec.push_back(i);
}
cout<<"Extended vector size : "<<vec.size()<<"\n";
for(i=0;i<5;i++)
{
cout<<"Value of vec ["<<i<<"] = "<<vec[i]<<"\n";
}
vector<int>::iterator v=vec.begin();
while(v!=vec.end()){
cout<<"Value of v = "<<*v<<"\n";
v++;
}
return 0;
}
/*
Array is collection of similar element
STL has predefine class array
like this
array<int,4> obj;
Here a array is formed with side 4
to use this you need to include array
template<place holder>
class array{
};
*/
#include<iostream>
#include<array>
using namespace std;
int main()
{
array<int,4> data1={2,5,6,7};
// use this extra array with swap
array<int,4> data2={1,4,5,9};
// we can also initilize it here
// like this
// array<int,4> data={2,5,6,8};}
// it show some error
// to fix it click on setting
// if you are using dev then check on tool comiler option read the error and copy it on genneral add by tick
cout<<data1.at(1)<<endl; // it show index array start from 0
cout<<data1[2]<<endl;
cout<<data1.front()<<endl;
cout<<data1.back()<<endl;
for(int i=0;i<=data1.size();i++)
{
cout<<data1[i]<<" ";
}
cout<<"\n";
data1.fill(10);
for(int i=0;i<=data1.size();i++)
{
cout<<data1[i]<<" ";
// to store 1 element in hole array
}
cout<<"\n";
// swap
data1.swap(data2);
for(int i=0;i<=data1.size();i++)
{
cout<<data1[i]<<" ";
}
cout<<"\n";
for(int i=0;i<=data2.size();i++)
{
cout<<data2[i]<<" ";
}
cout<<"\n";
// to find the size
cout<<data1.size();
}
Here is a refernce on getting started with the competitative progaramming: http://sportprogramming.blogspot.com/2014/07/getting-started-with-sport-of.html