LeetCode Top Interview 150
108. 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.
A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one.
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: [1,3] and [3,1] are both a height-balanced BSTs.
Constraints:
1 <= nums.length <= 104-104 <= nums[i] <= 104numsis sorted in a strictly increasing order.
Solution
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func sortedArrayToBST(num []int) *TreeNode {
return makeTree(num, 0, len(num)-1)
}
func makeTree(num []int, left, right int) *TreeNode {
if left > right {
return nil
}
mid := (left + right) / 2
midNode := &TreeNode{Val: num[mid]}
midNode.Left = makeTree(num, left, mid-1)
midNode.Right = makeTree(num, mid+1, right)
return midNode
}