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

Valence number of an atom is defined as the exact number of bonds the atom must form with other atoms. Given 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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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 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



Output:

Yes

Time complexity: O(1)

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