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

class graph
{
    int V;
    list<int> *adj;
    public:
    graph(int V)
    {
        this->V =V;
        adj = new list<int>[V];
    }
    void addEdge(int v, int w);
    void bfs(int s);
    void dfs(int s);
    
};

void graph::addEdge(int v, int w)
{
    adj[v].push_back(w);
}

void graph::bfs(int s)
{

    bool *visited = new bool[V];
    for(int i = 0; i < V; i++)
        visited[i] = false;
 
 
    list<int> queue;
 
  
    visited[s] = true;
    queue.push_back(s);
 

    list<int>::iterator i;
 
    while(!queue.empty())
    {
        
        s = queue.front();
        cout << s << " ";
        queue.pop_front();
 
       
        for (i = adj[s].begin(); i != adj[s].end(); ++i)
        {
            if (!visited[*i])
            {
                visited[*i] = true;
                queue.push_back(*i);
            }
        }
    }

}

void graph::dfs(int s)
{
    vector<bool> visited(V, false);
    stack<int> stack;
    stack.push(s);
    while (!stack.empty())
    {
        int s = stack.top();
        stack.pop();
        if (!visited[s])
        {
            cout<< s <<" ";
            visited[s] = true;
        }
        for (auto i=adj[s].begin(); i!=adj[s].end(); i++)
        {
            if (!visited[*i])
            {
                stack.push(*i);
            }
        }
    }
}



int main()
{
     int n;
     cout<<"enter the total no of vertex: ";
     cin>>n;
     graph obj(n);

     int e;
     cout<<"enter the total no of edge: ";
     cin>>e;
     for (int i =0; i<e ; i++)
     {
         int temp1, temp2;
         cout<<" enter the edge: ";
        cin>>temp1>>temp2;
        obj.addEdge(temp1, temp2);
     }

     cout<<"\nthe BFS of the given graph from vertex 0\n";
     obj.bfs(0);

     cout<<"\nthe DFS of the given graph from vertex 0\n";
     obj.dfs(0);


}
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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
}