108. Convert Sorted Array to Binary Search Tree

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

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example:

Given the sorted array: [-10,-3,0,5,9],One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:      0     / \   -3   9   /   / -10  5 题意：将排好序的数组构建成叶子深度相等的二叉树 代码如下：

/** * Definition for a binary tree node. * function TreeNode(val) { *     this.val = val; *     this.left = this.right = null; * } *//** * @param {number[]} nums * @return {TreeNode} */var sortedArrayToBST = function(nums) {    return helper(nums,0,nums.length-1);};var helper=function(root,left,right){    if(left>right) return null;    let mid=parseInt((left+right)/2);    let cur=new TreeNode(root[mid]);    cur.left=helper(root,left,mid-1);    cur.right=helper(root,mid+1,right);    return cur;}