#include<bits/stdc++.h>
#include<chrono>
using namespace std::chrono;
using namespace std;

void swap(int *a, int *b){
	int t = *a;
	*a = *b;
	*b = t;
}

int partition(vector<int> &arr, int low, int high){
	int piv = arr[high];
	int i = low-1;
	for(int j = low; j < high; j++){
		if(arr[j] < piv){
			i++;
			swap(&arr[i], &arr[j]);
		}
	}
	swap(&arr[i+1], &arr[high]);
	return i+1;
}

void quicksort(vector<int> &arr, int low, int high){
	if(low < high){
		int piv = partition(arr, low, high);
		quicksort(arr, low, piv-1);
		quicksort(arr, piv+1, high);
	}
}

int main(){
	int n;
	cout << "Enter the no. of elements: " << endl;
	cin >> n;
	vector<int> arr(n);
	cout << "Enter the elements of vector: " << endl;
	for(int i = 0; i < n; i++) cin >> arr[i];
	auto start = high_resolution_clock::now();
	quicksort(arr, 0, n-1);
	auto stop = high_resolution_clock::now();
	auto duration = duration_cast<nanoseconds>(stop - start);
	cout << "Using Quick Sort Algo: " << endl;
	for(int i = 0; i < n; i++) cout << arr[i] << " ";
	cout << endl << "Time taken : " << duration.count() << " ns";
	return 0;
}

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
}