For a chain e-mail, each mailer sends messages to two new people. Some recipients continue the chain, and some don't. No one gets the same message twice. Sometime later, there are a total of 1500 message recipients. (That means your graph model will have 1501 vertices because the initiator of the chain e-mail is not one of the 1500 recipients.) How many people received messages but did not mail anything? Suggestion: Use the formulas Number of vertices = 2 × Number of parents + 1 and Number of vertices = Number of parents + Number of leaves.
I would also like to see someone answer this question.
I have not seen a question like this before.
Vertice is any node in the graph.
Parent is a vertice that has at least one path out of it leading to another vertice.
Leaf is a vertice that is not a parent.
let P be the number of parents and L the number of leafs. The folks that didn't forward the email are the leafs.
V=1501 = 2P+ 1
V=1501 = P + L
L = 751
I still need to think about why this always works ...