关于javascript:二叉树的先中后序遍历非递归版

const binaryTree = {    val: 1,    left: {        val: 2,        left: {            val: 4,        },        right: {            val: 5,        }    },    right: {        val: 3,        left: {            val: 6,            left: {                val: 8            }        },        right: {            val: 7,        }    }}

1. 先序遍历

const preorder = (root) => {    if(!root) return    const stack = [root]    while(stack.length) {        const n = stack.pop()        console.log(n.val)        if (n.right) stack.push(n.right)        if (n.left) stack.push(n.left)    }}preorder(binaryTree)

2. 中序遍历

const inorder = (root) => {    if (!root) return    const stack = []    let p = root    while(stack.length || p) {        while(p) {            stack.push(p)            p = p.left        }        const n = stack.pop()        console.log(n.val)        p = n.right    }}inorder(binaryTree)

3. 后序遍历

const postorder = (root) => {    if (!root) return    const stack = [root]    const res = []    while(stack.length) {        const n = stack.pop()        res.push(n)        if (n.left) stack.push(n.left)        if (n.right) stack.push(n.right)    }    while(res.length) {        const n = res.pop()        console.log(n.val)    }}postorder(binaryTree)