solution(python): 108. Convert Sorted Array to Binary Search Tree

108. Convert Sorted Array to Binary Search Tree

Easy/108. Convert Sorted Array to Binary Search Tree/Solution.py

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+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):
+        if not nums:
+            return None
+        head = self.helper(nums, 0, len(nums) - 1)
+        return head
+
+    def helper(self, nums, low, high):
+        if low > high:
+            return None
+        mid = low + (high - low) // 2
+        node = TreeNode(nums[mid])
+        node.left = self.helper(nums, low, mid - 1)
+        node.right = self.helper(nums, mid + 1, high)
+        return node
+