print binary tree level by level in python
Here's my attempt, using recursion, and keeping track of the size of each node and the size of children.
class BstNode:
def __init__(self, key):
self.key = key
self.right = None
self.left = None
def insert(self, key):
if self.key == key:
return
elif self.key < key:
if self.right is None:
self.right = BstNode(key)
else:
self.right.insert(key)
else: # self.key > key
if self.left is None:
self.left = BstNode(key)
else:
self.left.insert(key)
def display(self):
lines, *_ = self._display_aux()
for line in lines:
print(line)
def _display_aux(self):
"""Returns list of strings, width, height, and horizontal coordinate of the root."""
# No child.
if self.right is None and self.left is None:
line = '%s' % self.key
width = len(line)
height = 1
middle = width // 2
return [line], width, height, middle
# Only left child.
if self.right is None:
lines, n, p, x = self.left._display_aux()
s = '%s' % self.key
u = len(s)
first_line = (x + 1) * ' ' + (n - x - 1) * '_' + s
second_line = x * ' ' + '/' + (n - x - 1 + u) * ' '
shifted_lines = [line + u * ' ' for line in lines]
return [first_line, second_line] + shifted_lines, n + u, p + 2, n + u // 2
# Only right child.
if self.left is None:
lines, n, p, x = self.right._display_aux()
s = '%s' % self.key
u = len(s)
first_line = s + x * '_' + (n - x) * ' '
second_line = (u + x) * ' ' + '\\' + (n - x - 1) * ' '
shifted_lines = [u * ' ' + line for line in lines]
return [first_line, second_line] + shifted_lines, n + u, p + 2, u // 2
# Two children.
left, n, p, x = self.left._display_aux()
right, m, q, y = self.right._display_aux()
s = '%s' % self.key
u = len(s)
first_line = (x + 1) * ' ' + (n - x - 1) * '_' + s + y * '_' + (m - y) * ' '
second_line = x * ' ' + '/' + (n - x - 1 + u + y) * ' ' + '\\' + (m - y - 1) * ' '
if p < q:
left += [n * ' '] * (q - p)
elif q < p:
right += [m * ' '] * (p - q)
zipped_lines = zip(left, right)
lines = [first_line, second_line] + [a + u * ' ' + b for a, b in zipped_lines]
return lines, n + m + u, max(p, q) + 2, n + u // 2
import random
b = BstNode(50)
for _ in range(50):
b.insert(random.randint(0, 100))
b.display()
Example output:
__50_________________________________________
/ \
________________________43_ ________________________99
/ \ /
_9_ 48 ____________67_____________________
/ \ / \
3 11_________ 54___ ______96_
/ \ \ \ / \
0 8 ____26___________ 61___ ________88___ 97
/ \ / \ / \
14_ __42 56 64_ 75_____ 92_
/ \ / / \ / \ / \
13 16_ 33_ 63 65_ 72 81_ 90 94
\ / \ \ / \
25 __31 41 66 80 87
/ /
28_ 76
\
29
class Node(object):
def __init__(self, value, left=None, right=None):
self.value = value
self.left = left
self.right = right
def printTree(node, level=0):
if node != None:
printTree(node.left, level + 1)
print(' ' * 4 * level + '-> ' + node.value)
printTree(node.right, level + 1)
t = Node(1, Node(2, Node(4, Node(7)),Node(9)), Node(3, Node(5), Node(6)))
printTree(t)
output:
-> 7
-> 4
-> 2
-> 9
-> 1
-> 5
-> 3
-> 6