// C++ code to implement Hill Cipher 
#include <iostream> 
using namespace std; 

// Following function generates the 
// key matrix for the key string 
void getKeyMatrix(string key, int keyMatrix[][3]) 
{ 
	int k = 0; 
	for (int i = 0; i < 3; i++) 
	{ 
		for (int j = 0; j < 3; j++) 
		{ 
			keyMatrix[i][j] = (key[k]) % 65; 
			k++; 
		} 
	} 
} 

// Following function encrypts the message 
void encrypt(int cipherMatrix[][1], 
			int keyMatrix[][3], 
			int messageVector[][1]) 
{ 
	int x, i, j; 
	for (i = 0; i < 3; i++) 
	{ 
		for (j = 0; j < 1; j++) 
		{ 
			cipherMatrix[i][j] = 0; 
		
			for (x = 0; x < 3; x++) 
			{ 
				cipherMatrix[i][j] += 
					keyMatrix[i][x] * messageVector[x][j]; 
			} 
		
			cipherMatrix[i][j] = cipherMatrix[i][j] % 26; 
		} 
	} 
} 

// Function to implement Hill Cipher 
void HillCipher(string message, string key) 
{ 
	// Get key matrix from the key string 
	int keyMatrix[3][3]; 
	getKeyMatrix(key, keyMatrix); 

	int messageVector[3][1]; 

	// Generate vector for the message 
	for (int i = 0; i < 3; i++) 
		messageVector[i][0] = (message[i]) % 65; 

	int cipherMatrix[3][1]; 

	// Following function generates 
	// the encrypted vector 
	encrypt(cipherMatrix, keyMatrix, messageVector); 

	string CipherText; 

	// Generate the encrypted text from 
	// the encrypted vector 
	for (int i = 0; i < 3; i++) 
		CipherText += cipherMatrix[i][0] + 65; 

	// Finally print the ciphertext 
	cout << " Ciphertext:" << CipherText; 
} 

// Driver function for above code 
int main() 
{ 
	// Get the message to be encrypted 
	string message = "HELLO HOW ARE YOU"; 

	// Get the key 
	string key = "HILLMAGIC"; 

	HillCipher(message, key); 

	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
}