leetcode: 110. Balanced Binary Tree
阿新 • • 發佈:2018-11-08
Difficulty
Easy.
Problem
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.
AC
class Solution():
def isBalanced(self, root):
if not root:
return True
else:
return abs( self.height(root.left) - self.height(root.right) ) <= 1 \
and self.isBalanced(root.left) and self.isBalanced(root.right)
def height(self, root):
if not root:
return 0
else:
return max( self.height( root.left), self.height(root.right) ) + 1