#include <iostream>
using namespace std;
// C++ program to Find the kth Permutation 
// Sequence of first n natural numbers 
// Function to find the index of number 
// at first position of 
// kth sequence of set of size n 
int findFirstNumIndex(int& k, int n) 
{ 

	if (n == 1) 
		return 0; 
	n--; 

	int first_num_index; 
	// n_actual_fact = n! 
	int n_partial_fact = n; 

	while (k >= n_partial_fact 
		&& n > 1) { 
		n_partial_fact 
			= n_partial_fact 
			* (n - 1); 
		n--; 
	} 

	// First position of the 
	// kth sequence will be 
	// occupied by the number present 
	// at index = k / (n-1)! 
	first_num_index = k / n_partial_fact; 

	k = k % n_partial_fact; 

	return first_num_index; 
} 

// Function to find the 
// kth permutation of n numbers 
string findKthPermutation(int n, int k) 
{ 
	// Store final answer 
	string ans = ""; 

	set<int> s; 

	// Insert all natural number 
	// upto n in set 
	for (int i = 1; i <= n; i++) 
		s.insert(i); 

	set<int>::iterator itr; 

	// Mark the first position 
	itr = s.begin(); 

	// subtract 1 to get 0 based indexing 
	k = k - 1; 

	for (int i = 0; i < n; i++) { 

		int index 
			= findFirstNumIndex(k, n - i); 

		advance(itr, index); 

		// itr now points to the 
		// number at index in set s 
		ans += (to_string(*itr)); 

		// remove current number from the set 
		s.erase(itr); 

		itr = s.begin(); 
	} 
	return ans; 
} 

// Driver code 
int main() 
{ 

	int n = 3, k = 4; 

	string kth_perm_seq 
		= findKthPermutation(n, k); 

	cout << kth_perm_seq << endl; 

	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
}