 #include <bits/stdc++.h>

using namespace std;

void dfs(int node , vector<vector<int>> astronaut , vector<int>&vis , int &count){
    vis[node] = 1;
    count++;
    for(auto it:astronaut[node]){
        if(!vis[it]){
            dfs(it,astronaut,vis,count);
        }
    }
}
int journeyToMoon(int n, vector<vector<int>> astronaut) {
    vector<int>sol(n);
    vector<int>vis(n,0);
    for(int i = 0 ; i < n ; i++){
        if(!vis[i]){
            int count = 0;
            dfs(i,astronaut,vis,count);
            sol.push_back(count);
        }
    }
    int val = (n*(n-1)/2);
    for(int i = 0 ; i < sol.size() ; i++){
        int x = (sol[i]*(sol[i]-1))/2;
        val = val - x;
    }
    return val;
}

int main()
{
    int v,e;
    cin>>v>>e;
    vector<vector<int>>astronaut(v);
    for(int i = 0 ; i < v ; i++){
        int x,y;
        cin>>x>>y;
        astronaut[x].push_back(y);
        astronaut[y].push_back(x);
    }
    int val = journeyToMoon(v,astronaut);
    cout<<val;
    return 0;
}

created 3 years ago by 32_it_subham sharma

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Read inputs from stdin

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#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
}