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,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.import com_github_leetcode.TreeNode
/*
* Example:
* var ti = TreeNode(5)
* var v = ti.`val`
* Definition for a binary tree node.
* class TreeNode(var `val`: Int) {
* var left: TreeNode? = null
* var right: TreeNode? = null
* }
*/
class Solution {
fun sortedArrayToBST(num: IntArray): TreeNode? {
/*1. Set up recursion*/
return makeTree(num, 0, num.size - 1)
}
private fun makeTree(num: IntArray, left: Int, right: Int): TreeNode? {
/*2. left as lowest# can't be greater than right*/
if (left > right) {
return null
}
/*3. Set median# as node*/
val mid = (left + right) / 2
val midNode = TreeNode(num[mid])
/*4. Set mid node's kids*/
midNode.left = makeTree(num, left, mid - 1)
midNode.right = makeTree(num, mid + 1, right)
/*5. Sends node back || Goes back to prev node*/
return midNode
}
}