EXPLAIN PLEASEEEE & I WILL UPVOTE

Ex.4 (Dealing with Constraints, DFS) Bob has to schedule n jobs. Unfortunately, each job may depend on other jobs that need to be completed first. For example job 13 may depend on job 42, in which case we first need to complete job 42 and only then we can start job 13 . Given the n jobs and a set of pairwise constraints (e.g. (13,42)), given an O(m+n) time algorithm that finds Figure 2: The Petersen Graph. Is it hamiltonian? Is it bipartite? Is it Eulerian? Is it 3 -colorable? a valid scheduling. (that is a scheduling in which a job starts only after we have completed jobs that it depends on.)