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Author: NinePiece2

Solutions/0108-convert-sorted-array-to-binary-search-tree/README.md

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+<p>Given an integer array <code>nums</code> where the elements are sorted in <strong>ascending order</strong>, convert <em>it to a </em><span data-keyword="height-balanced"><strong><em>height-balanced</em></strong></span> <em>binary search tree</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree1.jpg" style="width: 302px; height: 222px;" />
+<pre>
+<strong>Input:</strong> nums = [-10,-3,0,5,9]
+<strong>Output:</strong> [0,-3,9,-10,null,5]
+<strong>Explanation:</strong> [0,-10,5,null,-3,null,9] is also accepted:
+<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree2.jpg" style="width: 302px; height: 222px;" />
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree.jpg" style="width: 342px; height: 142px;" />
+<pre>
+<strong>Input:</strong> nums = [1,3]
+<strong>Output:</strong> [3,1]
+<strong>Explanation:</strong> [1,null,3] and [3,1] are both height-balanced BSTs.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>4</sup></code></li>
+	<li><code>-10<sup>4</sup> &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
+	<li><code>nums</code> is sorted in a <strong>strictly increasing</strong> order.</li>
+</ul>

Solutions/0108-convert-sorted-array-to-binary-search-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 sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
+        def dfs(left: int, right: int) -> Optional[TreeNode]:
+            if left > right:
+                return None
+            mid = (left + right) // 2
+            return TreeNode(nums[mid], dfs(left, mid - 1), dfs(mid + 1, right))
+
+        return dfs(0, len(nums) - 1)