leetcode Convert Sorted Array to Binary Search Tree

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Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

 

 1 /** 2  * Definition for binary tree 3  * public class TreeNode { 4  *     int val; 5  *     TreeNode left; 6  *     TreeNode right; 7  *     TreeNode(int x) { val = x; } 8  * } 9  */10 public class Solution {11     public TreeNode sortedArrayToBST(int[] num) {12         if (num==null || num.length==0) {13             return null;14         }15       int middle = num.length/2;  16       int[] firstarray= new int[middle];17       int[] secondarray = new int[num.length-1-middle];18       for (int i = 0; i < middle; i++) {19         firstarray[i]=num[i];20     }21       for (int i = 0; i <secondarray.length; i++) {22         secondarray[i]=num[middle+1+i];23     }24       TreeNode rootNode=new TreeNode(num[middle]);25       rootNode.left=sortedArrayToBST(firstarray);26       rootNode.right=sortedArrayToBST(secondarray);27       return rootNode;28     }29 }

 

leetcode Convert Sorted Array to Binary Search Tree