0108. Convert Sorted Array to Binary Search Tree.js

// 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

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {number[]} nums
 * @return {TreeNode}
 */
const sortedArrayToBST = (nums) => {
  if (!nums.length) return null;

  const m = ~~(nums.length / 2);

  const node = new TreeNode(nums[m]);
  node.left = sortedArrayToBST(nums.slice(0, m));
  node.right = sortedArrayToBST(nums.slice(m + 1));   // make sure + 1, because middle number is root node, so need skip it
  return node;
};