#include <iostream>
using namespace std;


//matrix representation
class Graph {
  private:
  bool** adjencyMatrix;
  int Vertices;  //No. of vertices

  public:
  Graph(int Vertices) {
    this->Vertices = Vertices;
    adjencyMatrix = new bool*[Vertices];
    for (int i = 0; i < Vertices; i++) {
      adjencyMatrix[i] = new bool[Vertices];
      for (int j = 0; j < Vertices; j++)
        adjencyMatrix[i][j] = false;
    }
  }
   
  //Function to add an edge into the graph
  void addEdge(int i, int j) {
    adjencyMatrix[i][j] = true;
    adjencyMatrix[j][i] = true;
  }

  void removeEdge(int i, int j) {
    adjencyMatrix[i][j] = false;
    adjencyMatrix[j][i] = false;
  }
  
  void toString() {
    for (int i = 0; i < Vertices; i++) {
      for (int j = 0; j < Vertices; j++)
        cout << adjencyMatrix[i][j] << " ";
      cout << "\n";
    }
  }

  ~Graph() {
    for (int i = 0; i < Vertices; i++)
      delete[] adjencyMatrix[i];
    delete[] adjencyMatrix;
  }
};

int main() {

  //get user input graph size 
  using namespace std;
  cout << "Graph size: " ; int a;
  cin >> a;
  Graph g(a);

  //get user input vertices
  cout << "\nGraph Vertices: ";
  char alpha[26] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L','M', 'N', 'O','P','Q','R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};


  for(int i = 0; i < a; i++){
      cout << " " << alpha[i] << " ";
  }
  
  //get user input graph 
  cout << "\n\nDirected or Undirected?"
            "\n0 - Directed"
            "\n1 - Undirected"<<endl;
            cout<< "Graph:";
        int choice; cin >> choice;
        cout << endl<<endl;
  
  //determine connections(source and destination node)
  cout << "\nGraph connections:"<< a << endl;
  for(int i =0; i < a; i ++){
      int iS, iD;
      
      cout << "S: "; char S; cin >> S;
      for(int j = 0; j < 26; j++){
          if(alpha[j] == S){
              iS = j;
              break;
          }
      }

      cout << "D: "; char D; cin >> D;
      for(int j = 0; j < 26; j++){
          if(alpha[j] == D){
              iD = j;
              break;
            
              
          }
      }
      g.addEdge(iS, iD);
  }
  //graph representation
  cout << "\nAdjency Matrix:";
  cout << endl;
  g.toString();
}

C++ Online Compiler

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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
}