#include <iostream>
using namespace std;
void merge(int *,int, int , int );
void merge_sort(int *arr, int low, int high)
{
    int mid;
    if (low < high){
        //divide the array at mid and sort independently using merge sort
        mid=(low+high)/2;
        merge_sort(arr,low,mid);
        merge_sort(arr,mid+1,high);
        //merge or conquer sorted arrays
        merge(arr,low,high,mid);
    }
}
// Merge sort 
void merge(int *arr, int low, int high, int mid)
{
    int i, j, k, c[50];
    i = low;
    k = low;
    j = mid + 1;
    while (i <= mid && j <= high) {
        if (arr[i] < arr[j]) {
            c[k] = arr[i];
            k++;
            i++;
        }
        else  {
            c[k] = arr[j];
            k++;
            j++;
        }
    }
    while (i <= mid) {
        c[k] = arr[i];
        k++;
        i++;
    }
    while (j <= high) {
        c[k] = arr[j];
        k++;
        j++;
    }
    for (i = low; i < k; i++)  {
        arr[i] = c[i];
    }
}
// read input array and call mergesort
int main()
{
    int myarray[30], num;
    char n[30];
    char r[10];
    cout<<"Enter the Name.....";
    cin>>n;
    cout<<"Enter the Rollno.....";
    cin>>r;
    cout<<"Enter number of elements to be sorted:";
    cin>>num;
    cout<<"Enter "<<num<<" elements to be sorted:";
    for (int i = 0; i < num; i++) { cin>>myarray[i];
    }
    merge_sort(myarray, 0, num-1);
    cout<<"Sorted array\n";
    for (int i = 0; i < num; i++)
    {
        cout<<myarray[i]<<"\t";
    }
}

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

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
}