shortest vertex path...needs work

The task is to use breadth-first search to compute single-source shortest distances in an unweighted directed graph.

Given: A simple directed graph with n≤103 vertices in the edge list format.

Return: An array D[1..n] where D[i] is the length of a shortest path from the vertex 1 to the vertex i (D[1]=0). If i is not reachable from 1 set D[i] to −1.

See Figure 1 for visual example from the sample dataset.