Return the root node of a binary search tree that matches the given preorder traversal.
So basically return a Binary Search Tree from an array of elements that are in preorder
For a binary search tree at any given nodeany descendant of node.left < node.val and any descendant of node.right > node.val
Algorithm:
- Loop through each element
- find the leaf node to insert
- repeat
Code:
/** * Definition for a binary tree node. * function TreeNode(val, left, right) { * this.val = (val===undefined ? 0 : val) * this.left = (left===undefined ? null : left) * this.right = (right===undefined ? null : right) * } */ /** * @param {number[]} preorder * @return {TreeNode} */ var bstFromPreorder = function(preorder) { let root = new TreeNode(preorder[0]) for(let i = 1; i < preorder.length; i++) { root = insert(root, preorder[i]) } return root }; var insert = function(node, elem) { if(!node) return new TreeNode(elem) if(node.val > elem) { node.left = insert(node.left, elem) } else { node.right = insert(node.right, elem) } return node } 
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