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

void add(vector<int> adj[],int u,int v){
  adj[u].push_back(v);
  adj[v].push_back(u);
}

void printGraph(vector<int> adj[],int N){
  for(int i=1;i<=N;i++){
    cout<<i;
    for(auto j:adj[i]){
      cout<<'-'<<j;
    }
    cout<<'\n';
  }
}

bool iscyclebfs(vector<int> adj[],vector<int> vis,int N,int n){
  queue<pair<int,int>> q;
  q.push({n,-1});
  vis[n]=1;
  while(!q.empty()){
    int node = q.front().first;
    int par = q.front().second;
    q.pop();
    for(auto i: adj[node]){
      if(!vis[i]){
        q.push({i,node});
        vis[i]=1;
      } else {
        if(i!=par){
          return true;
        }
      }
    }
  }
  return false;
}

bool iscycle(vector<int> adj[],int N){
  vector<int> vis(N+1,0);
  for(int i=1;i<=N;i++){
    if(!vis[i]){
      if(iscyclebfs(adj,vis,N,i)){
        return true;
      }
    }
  }
  return false;
}

int main(){
  int N=11;
  vector<int> adj[N+1];
  add(adj,1,2);
  add(adj,2,4);
  add(adj,3,5);
  add(adj,5,10);
  add(adj,5,6);
  add(adj,10,9);
  add(adj,6,7);
  add(adj,9,8);
  add(adj,7,8);
  add(adj,8,11);
  printGraph(adj,N);
  
  if(iscycle(adj,N)){
    cout<<"Yes ,there is a cycle";
  } else {
    cout<<"No cycle found";
  }
}
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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
}