[LeetCode] Convert Sorted Array to Binary Search Tree

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

[Solution].java

/**
 * 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
        return build(num, 0, num.length - 1);
    }

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