Seems that we should construct a complete binary tree.
from queue import *
class binary_tree_node:
def __init__(self, value = None):
self.value = value
self.left = None
self.right = None
def construct_min_btree(array):
# Keep track of current element in the array
i = 0
# Construct while doing BFS
q = queue()
root = binary_tree_node(array[i])
i += 1
q.enqueue(root)
while not q.is_empty():
n = q.dequeue()
# Construct left child
n.left = binary_tree_node(array[i])
i += 1
if i == len(array):
break
q.enqueue(n.left)
# Construct right child
n.right = binary_tree_node(array[i])
i += 1
if i == len(array):
break
q.enqueue(n.right)
return root
# Test case
if __name__ == "__main__":
array = [i for i in range(0, 80)]
root = construct_min_btree(array)
# Print the binary tree in level-order
q = queue()
q.enqueue(root)
current_level = 0
num_in_current_level = 2**current_level
while not q.is_empty():
n = q.dequeue()
print n.value,
if n.left != None:
q.enqueue(n.left)
if n.right != None:
q.enqueue(n.right)
num_in_current_level -= 1
# End of a level
if num_in_current_level == 0:
current_level += 1
num_in_current_level = 2**current_level
print "\n"The solution on the answer page constructs a binary search tree with recursion.
from queue import *
class binary_tree_node:
def __init__(self, value = None):
self.value = value
self.left = None
self.right = None
def construct_min_btree(array, start, end):
if start > end:
return
mid = (start + end)/2
n = binary_tree_node(array[mid])
n.left = construct_min_btree(array, start, mid - 1)
n.right = construct_min_btree(array, mid + 1, end)
return n
# Test case
if __name__ == "__main__":
array = [i for i in range(0, 8)]
root = construct_min_btree(array, 0, 7)
# Print the binary tree in level-order
q = queue()
q.enqueue(root)
current_level = 0
num_in_current_level = 2**current_level
while not q.is_empty():
n = q.dequeue()
print n.value,
if n.left != None:
q.enqueue(n.left)
if n.right != None:
q.enqueue(n.right)
num_in_current_level -= 1
# End of a level
if num_in_current_level == 0:
current_level += 1
num_in_current_level = 2**current_level
print "\n"