Performing Breadth First Search recursively

Question

Let\'s say you wanted to implement a breadth-first search of a binary tree recursively. How would you go about it?

Is it possible using only the call-stack

Answer 1

Let v be the starting vertex

Let G be the graph in question

The following is the pseudo code without using queue

Initially label v as visited as you start from v
BFS(G,v)
    for all adjacent vertices w of v in G:
        if vertex w is not visited:
            label w as visited
    for all adjacent vertices w of v in G:
        recursively call BFS(G,w)