This is a C program based on the Graphical Sequence Algorithm from my Graph Theory class. The notes are as followed:

Graphical Sequence Algorithm
Input: A sequence s of p integers in decreasing order
Output: Yes if s is graphical
        No if s is not graphical
1. If some integer s exceed |s| - 1 = p -1 then stop and say No.
2. If each term of s is 0, then stop and say Yes.
3. If some integer is negative, then sto pand say No.
4. Delete the first term, n, from the sequence and then subtract one from the next n terms to get a new sequence.
5. List the new sequence in decreasing order (if necessary) and then go to 2.