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108. Convert Sorted Array to Binary Search Tree

Problem Statement

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

Go

package main

// Definition for a binary tree node.
type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func sortedArrayToBST(nums []int) *TreeNode {
	if len(nums) == 0 {
		return nil
	}

	return contructBST(nums, 0, len(nums)-1)
}

func contructBST(nums []int, left, right int) *TreeNode {
	if left > right {
		return nil
	}

	mid := (left + right) / 2
	node := &TreeNode{Val: nums[mid]}
	node.Left = contructBST(nums, left, mid-1)
	node.Right = contructBST(nums, mid+1, right)
	return node
}

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