后序遍历

递归实现后序遍历

// 递归实现二叉树后序遍历
function postOrderTraverse(root) {
  if (!root) return
 
  postOrderTraverse(root.left)
  postOrderTraverse(root.right)
  console.log(root.val)
}

迭代实现后续遍历

// 迭代实现二叉树后序遍历
function postOrderTraverse(root) {
  const result = []
  if (!root) return
 
  const stack = []
  stack.push(root)
 
  while (stack.length) {
    const top = stack.pop()
    result.unshift(top.val)
 
    if (top.left) {
      stack.push(top.left)
    }
 
    if (top.right) {
      stack.push(top.right)
    }
  }
 
  return result
}