#### 构造树并判断是否对称

``````class Node {
constructor (val) {
this.val = val
this.left = this.right = undefined
}
}
class Tree {
constructor (data) {
// 临时存储所有节点
let nodeList = []
// 根节点
let root
for (let i = 0, len = data.length; i < len; i++) {
let node = new Node(data[i])
nodeList.push(node)
if (i > 0) {
// 记录当前节点属于哪一层
let n = Math.floor(Math.sqrt(i + 1))
// 记录当前层的起始点
let q = Math.pow(2, n) - 1
// 记录上一层的起始点
let p = Math.pow(2, n - 1) - 1
let parent = nodeList[p + Math.floor((i - q) / 2)]
// 将当前节点和上一层的父节点做关联
if (parent.left) {
parent.right = node
} else {
parent.left = node
}
}
}
root = nodeList.shift()
nodeList.length = 0
return root
}
static isSymmetry (root) {
if (!root) {
return true
}
let walk = (left, right) => {
if (!left && !right) {
return true
}
if ((left && !right) || (!left && right) || (left.val !== right.val)) {
return false
}
return walk(left.left, right.right) && walk(left.right, right.left)
}
return walk(root.left, root.right)
}
}

export default Tree

export {
Node
}
``````