feat(alternative): add balance binary tree solution in python

Author: bujosa

alternative/easy/balance_binary_tree.py

@@ -0,0 +1,44 @@
+class TreeNode:
+ def __init__(self, x):
+ self.val = x
+ self.left = None
+ self.right = None
+
+def is_balanced(root):
+ def height(node):
+ if not node:
+ return 0
+ left_height = height(node.left)
+ right_height = height(node.right)
+ if left_height == -1 or right_height == -1 or abs(left_height - right_height) > 1:
+ return -1
+ return max(left_height, right_height) + 1
+
+ return height(root) != -1
+
+# Test cases
+t1 = TreeNode(3)
+t2 = TreeNode(9)
+t3 = TreeNode(20)
+t4 = TreeNode(15)
+t5 = TreeNode(7)
+t2.left = t4
+t2.right = t5
+t1.left = t2
+t1.right = t3
+assert is_balanced(t1) == True
+
+t1 = TreeNode(1)
+t2 = TreeNode(2)
+t3 = TreeNode(2)
+t4 = TreeNode(3)
+t5 = TreeNode(3)
+t6 = TreeNode(4)
+t7 = TreeNode(4)
+t6.left = t7
+t5.left = t6
+t4.left = t5
+t3.left = t4
+t2.left = t3
+t1.left = t2
+assert is_balanced(t1) == False