Convert Sorted Array to Binary Search Tree

/** * 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) { if(!nums.length) return null; const result = new TreeNode(nums) return result }; function TreeNode(nums) { if(nums.length){ const middleIndex = Math.floor(nums.length/2)
        this.val = nums[middleIndex]; if(middleIndex>0){ this.left =  new TreeNode(nums.slice(0, middleIndex)); } else { this.left =  null } if(middleIndex<nums.length-1){ this.right = new TreeNode(nums.slice(middleIndex+1)); } else { this.right = null } } else { return null } }

上面是将有序数组转为二叉树的代码～

二分查找的速度为O(log n)， 遍历二叉树的速度为O(n)