From these interviews, they’ve learned about a set of n people (all of them now decreased), whom we’ll denote
P1,P2,..., Pn. They’ve also collected facts about when these people lived relative to one another. Each fact has one of the following two froms:
• For some i and j, person Pi died before person Pj was born;
• for some i and j, the life spans of Pi and Pj overlapped at least partially.
Naturally, they’re not sure that all these facts are correct; memories are not so good,
and a lot of this was passed down by word of mouth. So what they’d like you to determine is whether the data they’ve collected is at least internally consistent, in the sense that there could have existed a set of people for which all the facts they’ve learned simultaneously hold.
Give an effective algorithm to do this: either it should produce proposed dates of birth and death for each of the n people so that all the facts hold true, or it should report (correctly) that no such dates can exist – that is, the facts collected by the
ethnographers are not internally consistent.