[LeetCode Sync] Runtime - 8 ms (18.75%), Memory - 19.1 MB (7.02%)

Author: NamVr

0110-balanced-binary-tree/README.md

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+<p>Given a binary tree, determine if it is <span data-keyword="height-balanced"><strong>height-balanced</strong></span>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_1.jpg" style="width: 342px; height: 221px;" />
+<pre>
+<strong>Input:</strong> root = [3,9,20,null,null,15,7]
+<strong>Output:</strong> true
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_2.jpg" style="width: 452px; height: 301px;" />
+<pre>
+<strong>Input:</strong> root = [1,2,2,3,3,null,null,4,4]
+<strong>Output:</strong> false
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> root = []
+<strong>Output:</strong> true
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the tree is in the range <code>[0, 5000]</code>.</li>
+	<li><code>-10<sup>4</sup> &lt;= Node.val &lt;= 10<sup>4</sup></code></li>
+</ul>

0110-balanced-binary-tree/solution.py

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+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isBalanced(self, root: Optional[TreeNode]) -> int:
+        def dfs(root):
+            if not root: return [True, 0]
+            # [is the tree balanced? , height of tree]
+
+            left, right = dfs(root.left), dfs(root.right)
+
+            balanced = left[0] and right[0] and abs(left[1] - right[1]) <= 1
+            return [balanced, 1 + max(left[1], right[1])]
+
+        return dfs(root)[0]