Breadth first search

Breadth first search --- поиск в ширину.

Given the adjacency lists [math]\displaystyle{ A(v) }[/math] for each vertex [math]\displaystyle{ v }[/math] of a connected graph (directed or undirected), the following algorithm conducts a breadth first search. On completion of the search, each vertex has acquired a breadth first index (BFI) indicating the order in which the vertex was visited. The vertex [math]\displaystyle{ u }[/math] is visited first and [math]\displaystyle{ BFI(u) = 0 }[/math].