LeetCode:Convert Sorted Array to Binary Search Tree

Convert Sorted Array to Binary Search Tree

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

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedArrayToBST(int[] num) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(num.length==0) return null;
        return sortedArrayToBST(num,0,num.length-1);
    }
     
    public TreeNode sortedArrayToBST(int[] num, int start, int end){
        if(start>end) return null;
        int mid=(start+end)/2;
        TreeNode res = new TreeNode(num[mid]);
        res.left=sortedArrayToBST(num,start,mid-1);
        res.right=sortedArrayToBST(num,mid+1,end);
        return res;
    }
}