108. Convert Sorted Array to Binary Search Tree

📋 Đề Bài

Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

Example 1:

Input: nums = [-10,-3,0,5,9]
Output: [0,-3,9,-10,null,5]
Explanation: [0,-10,5,null,-3,null,9] is also accepted:

Example 2:

Input: nums = [1,3]
Output: [3,1]
Explanation: [1,null,3] and [3,1] are both height-balanced BSTs.

Constraints:

1 <= nums.length <= 10⁴
-10⁴ <= nums[i] <= 10⁴
nums is sorted in a strictly increasing order.

🧠 Thuật Toán & Kỹ Thuật

Binary Search (Tìm kiếm nhị phân)Tree Traversal (Duyệt cây)

⏱️ Thời gian O(log n)

💾 Không gian O(n)

💻 Lời Giải

Python 0108-convert-sorted-array-to-binary-search-tree.py

# 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]:
        if not nums:
            return None
        
        mid = len(nums) // 2
        
        node = TreeNode(nums[mid])
        
        node.left = self.sortedArrayToBST(nums[:mid])
        node.right = self.sortedArrayToBST(nums[mid + 1:])
        
        return node