二叉树的遍历

前序遍历

function prePrint(root){
    if(root){
        console.log(root.val)
        prePrint(root.left)
        prePrint(root.right)
    }
}

中序遍历

function prePrint(root){
    if(root){
        prePrint(root.left)
        console.log(root.val)
        prePrint(root.right)
    }
}

后序遍历

function prePrint(root){
    if(root){
        prePrint(root.left)
        prePrint(root.right)
        console.log(root.val)
    }
}

层序遍历

function sequenceTraversal(root){
    if (!this.root) {
        return
    }
    let q = []
    q.push(this.root)
    while (q.length>0) {
        let t = q.shift()
        console.log(t.value)
        if (t.left) q.push(t.left)
        if (t.right) q.push(t.right)
    }
}