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

// printing vectors of pairs

void printvp( vector<pair<int,int>> &v){
  
  cout << "size: " << v.size() << "\n";
  
  for(int i=0; i<v.size(); i++){
    
    cout << v[i].first << " " << v[i].second << "\n";
  }
  cout << "\n";
}

// printing arrays of vectors

void printvec( vector<int> &v){
  
  cout << "size: " << v.size() <<  "\n" ;
  
  for(int i=0; i<v.size(); i++){
    cout << v[i] << " ";
  }
  cout << "\n";
}

int main() 
{
   /*     //  VECTOR OF PAIR
   
  //    vector<pair<int,int>> v= { {1,2}, {2,3} , {4,5} } ;    for initializing the values
  //   printvec(v);
    
    vector<pair<int,int>> v;
    
    int n;
    cin>>n;
    
    for(int i=0; i<n; i++){
      
      int x, y;
      cin>>x>>y;    // taking the values of the pair of vector
      
      v.push_back({x,y}) ; // v.push_back(make_pair(x,y)) ;
    }
    
    printvp(v);
    
  */
  
/*
              ARRAY OF VECTORS
              
  int N;
  cin>>N;
  
  vector<int> v[N] ;
  
  for(int i=0; i<N; i++){
    
    int n;
    cin>>n;
    
    for(int j=0; j<n; j++){
      int x;
      cin>>x;
      v[i].push_back(x);
    }
  }
  
  for( int i=0; i<N; i++){
    
    printvec(v[i])  ;
  }
  
    cout << v[0][1] ;  // its behaving like 2d array

*/

//              VECTOR OF VECTOR


int N;
cin>>N;

vector<vector<int>> v;

for(int i=0; i<N; i++){
  
  int n;
  cin>>n;
  
   vector<int> temp;
  
  for( int j=0; j<n; j++){
    
    int x;
    cin>>x;
    
    temp.push_back(x);
    
  }
  
  v.push_back(temp);
}


for(int i=0; i<v.size(); i++){
  
  printvec(v[i]);
}
  cout << v[0][1] ;
  
    return 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
}