// CPP program to illustrate
// Initializing of pair STL
#include <iostream>
#include <utility>
using namespace std;

int main()
{

//pair<string, double> PAIR2{"GeeksForGeeks", 1.23};
//pair<string, double> PAIR2("GeeksForGeeks", 1.23);
//
//	cout << PAIR2.first << " ";
//	cout << PAIR2.second << endl;

	//return 0;
	
	//pair<string,double>PAIR3=make_pair("mukh",5.43);
	//cout<<PAIR3.first<<endl;
	//cout<<PAIR3.second<<endl;
	//pair<int,int>PAIR4=make_pair(34,54);
	//pair<int,int>PAIR5=make_pair(32,54);
	//if(PAIR4.second==PAIR5.second)
	//cout<<"same"<<endl;
//
//pair<int, pair<int, char> > pair3 = { 3, { 4, 'a' } };
//    int x, y;
//    char z;
//     
//    // tie(x,y,z) = pair3; Gives compilation error
//    // tie(x, tie(y,z)) = pair3; Gives compilation error
//    // Each pair needs to be explicitly handled
//    x = pair3.first;
//    tie(y, z) = pair3.second;
//    cout << x << " " << y << " " << z << "\n";  } 
    pair<int,int>PAIR8={1,2};
    pair<int,int>PAIR9={2,3};
    swap(PAIR9,PAIR8);
    cout<<PAIR8.first<<" "<<PAIR8.second<<endl;}
by

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}