증가하는 주문 검색 트리

/**
 * 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 {TreeNode} root
 * @return {TreeNode}
 */
var increasingBST = function(root) {
    let nodes = []
    dfs(root)

    let treeNode = new TreeNode(0)
    let current = treeNode
    for(let i = 0; i < nodes.length; i++) {
        current.right = new TreeNode(nodes[i])
        current = current.right
    }

    return treeNode.right

    function dfs(root) {
        if(root != null) {
            dfs(root.left)
            nodes.push(root.val)
            dfs(root.right)
        }
    }   
};