print a binary tree of integers in level order. Level-order printing means printing each row of the tree from left to right, from root row to the deepest row. After each row, print a newline.

gistfile1.py

import Queue

class tr:
	def __init__(self,val=None,children=None):
		self.val=val
		self.children=children or []

def emit_level_order(tree):
	cur_level = 0
	q = Queue.Queue()
	q.put((0,tree))

	while True:
		try:
			(level, subt) = q.get_nowait()
		except Queue.Empty:		
			break
		
		if level > cur_level:
			print
			cur_level += 1
		print "%s " % subt.val,
		for child in subt.children:
			q.put_nowait((level+1, child))
	print
	
print "Binary"
emit_level_order(tr(3, [tr(9),tr(20,[tr(15),tr(7)])]))
print "K-ary"
emit_level_order(tr(3, [tr(9),tr(20,[tr(15),tr('k2'),tr(7)]), tr('knary')]))


$ python ./tree.py 
Binary
3 
9  20 
15  7 
K-ary
3 
9  20  knary 
15  k2  7