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

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

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题解：递归就可以了。

Java代码如下：

/**
 * 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) {
        return Helper(num, 0, num.length-1);
    }
    public TreeNode Helper(int[] num,int begin,int end){
        if(begin > end)
            return null;
        
        int mid = (begin + end)/2;
        TreeNode root = new TreeNode(num[mid]);
        root.left = Helper(num, begin, mid-1);
        root.right = Helper(num, mid+1, end);
        return root;
    }
}