Convert Sorted Array to Binary Search Tree

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] <= 104
  • nums is sorted in a strictly increasing order.

Solution

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public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode() {}
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}

class Solution {
private TreeNode sortedArrayToBST(int[] nums, int p, int q) {
if(p > q) return null;
int mid = (q + p) / 2;
TreeNode node = new TreeNode(nums[mid]);
node.left = sortedArrayToBST(nums,p, mid -1);
node.right = sortedArrayToBST(nums, mid + 1, q);
return node;
}
public TreeNode sortedArrayToBST(int[] nums) {
return sortedArrayToBST(nums, 0, nums.length - 1);
}
}