Hi. I have encountered this problem recently and didn't know how to approach it.
We want to construct compounds with these properties:
C
has 4 links and can bond with eitherC
,H
orI
H
can bond withC
only through 1 linkI
can bond withC
only through 2 links- there is no atom with one or more free links
For example, H-C=C
is not a compound because the middle C
needs another link and the right one 2 more.
Two compounds are different if the numbers of C
, H
or I
differ.
Now we define the mass of a compound as 4 * no. of C + 2 * no. of I + no. of H
.
Task
Given 30 <= N <= 100000
, find how many compounds with mass N
there are with at least one C
, I
and H
.
Example:
Input: N = 40
Output: 3
Explanation
These are the only possible compounds with mass 40
: