Question

I figured out Depth First Traversal for a Tree.

def _dfs(tree, res):
    if tree:
        res += [tree.key]
        _dfs(tree.left, res)
        _dfs(tree.right, res)
    return res

I can’t seem to find a solution for Breadth First Search. Will one have to use queues or stacks?

Thanks!!

Answer 1

Yes, you’ll have to use a queue to hold nodes which you’ve checked but have yet to recurse into.

Start with the root node in the queue, then repeat [pop a node and for each of its children, perform whatever action you need (res += [tree.key]) and push it on the queue].