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LC_Balanced_Binary_Tree.py
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LC_Balanced_Binary_Tree.py
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"""
110. Balanced Binary Tree
Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as:
a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example 1:
Given the following tree [3,9,20,null,null,15,7]:
3
/ \
9 20
/ \
15 7
Return true.
Example 2:
Given the following tree [1,2,2,3,3,null,null,4,4]:
1
/ \
2 2
/ \
3 3
/ \
4 4
Return false.
"""
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def isBalanced(self, root):
"""
:type root: TreeNode
:rtype: bool
"""
def rec_traverse (node):
if (node == None):
return [True, 0]
left = rec_traverse(node.left)
right = rec_traverse(node.right)
if (left[0]== False) or (right[0] == False):
return [False,-1]
if (abs(left[1]-right[1]) > 1):
return [False,-1]
else:
return [True,1+max(left[1],right[1])]
retval = rec_traverse(root)
if (retval[0] == True):
return True
return False