【leetcode刷题笔记】Convert Sorted Array to Binary Search Tree

 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         return Helper(num, 0, num.length-1);
13     }
14     public TreeNode Helper(int[] num,int begin,int end){
15         if(begin > end)
16             return null;
17         
18         int mid = (begin + end)/2;
19         TreeNode root = new TreeNode(num[mid]);
20         root.left = Helper(num, begin, mid-1);
21         root.right = Helper(num, mid+1, end);
22         return root;
23     }
24 }