Convert Sorted Array to Binary Search Tree - LeetCode 108

 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.

 

Solution(Only function):

/**

 * Definition for a binary tree node.

 * 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 {

    public TreeNode sortedArrayToBST(int[] nums) {

     if(nums.length==0) return null;

        

    

    return function(nums,0,nums.length-1);

    }

    public TreeNode function(int[] nums,int left,int right){

        

        if(left>right) return null;

        

        int mid=left+(right-left)/2;

        

        TreeNode node=new TreeNode(nums[mid]);

        node.left=function(nums,left,mid-1);

        node.right=function(nums,mid+1,right);

        

        return node;

        

    }

}