二叉树递归非递归前中后

preorder(node)
  if node == null then return
  visit(node)
  preorder(node.left) 
  preorder(node.right)
iterativePreorder(node)
  parentStack = empty stack
  parentStack.push(null)
  top =  node 
  while ( top != null )
      visit( top )
      if ( top.right != null ) 
          parentStack.push(top.right)
      if ( top.left != null ) 
          parentStack.push(top.left)
      top = parentStack.top();
      parentStack.pop();

In-order[edit]

inorder(node)
  if node == null then return
  inorder(node.left)
  visit(node)
  inorder(node.right)
iterativeInorder(node)
  parentStack = empty stack
  while (not parentStack.isEmpty() or node ≠ null)
    if (node ≠ null)
      parentStack.push(node)
      node = node.left
    else
      node = parentStack.pop()
      visit(node)
      node = node.right

Post-order[edit]

postorder(node)
  if node == null then return
  postorder(node.left)
  postorder(node.right)
  visit(node)
iterativePostorder(node)
  parentStack = empty stack  
  lastnodevisited = null 
  while (not parentStack.isEmpty() or node ≠ null)
    if (node ≠ null)
      parentStack.push(node)
      node = node.left
    else
      peeknode = parentStack.peek()
      if (peeknode.right ≠ null and lastnodevisited ≠ peeknode.right) 
        /* if right child exists AND traversing node from left child, move right */
        node = peeknode.right
      else
        parentStack.pop() 
        visit(peeknode)
        lastnodevisited = peeknode
原文地址:https://www.cnblogs.com/cavehubiao/p/3611186.html