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108. Convert Sorted Array To Binary Search Tree

Array Divide and Conquer Tree Binary Search Tree Binary Tree

Problem - Convert Sorted Array To Binary Search Tree

Easy

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.

Solutions

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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)

Submission Stats:

  • Runtime: 3 ms (70.62%)
  • Memory: 19.1 MB (59.86%)