LC- 从前序与中序遍历序列构造二叉树(JavaScript实现)

/*
 * @lc app=leetcode.cn id=105 lang=javascript
 *
 * [105] 从前序与中序遍历序列构造二叉树
 */

// @lc code=start
/**
 * 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
 * @param {number[]} inorder
 * @return {TreeNode}
 */
var buildTree = function(preorder, inorder) {
    if(preorder.length==0 || inorder.length==0) 
        return null;
    let root = preorder.shift();
    let pos = inorder.indexOf(root);
    let node = new TreeNode(root);
    node.left = buildTree(preorder.slice(0,pos),inorder.slice(0,pos))
    node.right=buildTree(preorder.slice(pos),inorder.slice(pos+1))
    return node;
};
// @lc code=end