Find if a molecule can be formed from 3 atoms using their valence numbers

The valence number of an atom is defined as the exact number of bonds the atom must form with other atoms. Given the valence number of 3 atoms, the task is to determine if they can form a molecule together or not. Atoms can form multiple bonds with each other. 

Examples:

Input: 2 4 2
Output: YES
The bonds are between the following atoms:
1 - 2
1 - 2
2 - 3
2 - 3

Input: 1 2 3
Output: NO 

Approach: Let the valence numbers be a, b and c. Let c be the largest. We have 2 cases in which the molecule cannot be formed:  

• a+b+c is odd: Since every bond decreases the valence number of 2 atoms by 1, the sum of valence numbers should be an even number.
• a+b < c: In this case, c will be left unsatisfied even if every bond is formed with it.

Below is the implementation of the above approach: 

C++

// C++ implementation of the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to check if it is possible
void printPossible(int a, int b, int c)
{
    if ((a + b + c) % 2 != 0 || a + b < c)
        cout << "NO";
    else
        cout << "YES";
}

// Driver code
int main()
{
    int a = 2, b = 4, c = 2;
    printPossible(a, b, c);

  return 0;
}

Java

// Java implementation of the above approach

import java.io.*;

class GFG {
    // Function to check if it is possible
static void printPossible(int a, int b, int c)
{
    if ((a + b + c) % 2 != 0 || a + b < c)
        System.out.println("NO");
    else
        System.out.println("YES");
}

// Driver code
    public static void main (String[] args) {

    int a = 2, b = 4, c = 2;
    printPossible(a, b, c);
    }
}

// This code is contributed by akt_mit

Python3

# Python 3 implementation of the
# above approach

# Function to check if it is possible
def printPossible( a, b, c):

    if ((a + b + c) % 2 != 0 or a + b < c):
        print ("NO")
    else:
        print ("YES")

# Driver code
if __name__ == "__main__":

    a = 2
    b = 4
    c = 2
    printPossible(a, b, c)

# This code is contributed
# by ChitraNayal

C#

// C# implementation of the above approach
using System;

class GFG
{

// Function to check if it is possible
static void printPossible(int a, int b, int c)
{
    if ((a + b + c) % 2 != 0 || a + b < c)
        Console.Write("NO");
    else
        Console.Write("YES");
}

// Driver code
public static void Main()
{
    int a = 2, b = 4, c = 2;
    printPossible(a, b, c);
}
}

// This code is contributed
// by Akanksha Rai

PHP

<?php
// PHP implementation of the above approach

// Function to check if it is possible
function printPossible($a, $b, $c)
{
    if (($a + $b + $c) % 2 != 0 ||
         $a + $b < $c)
        echo ("NO");
    else
        echo ("YES");
}

// Driver code
$a = 2;
$b = 4;
$c = 2;
printPossible($a, $b, $c);

// This code is contributed
// by Shivi_Aggarwal
?>

Javascript

<script>
    // Javascript implementation of the above approach

    // Function to check if it is possible
    function printPossible(a, b, c)
    {
        if ((a + b + c) % 2 != 0 || a + b < c)
            document.write("No");
        else
            document.write("Yes");
    }

    let a = 2, b = 4, c = 2;
    printPossible(a, b, c);

</script>

Output:

Yes

Time complexity: O(1)

Auxiliary Space: O(1)