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