复制二叉树（非递归实现）:

pbinary_tree_node copy_binary_tree(pbinary_tree_node bt)
{//先序遍历输出一颗树的全部结点值1,2,3
stack stack_left,stack_right;
pbinary_tree_node newbt;
if (bt!=NULL)
{
//new root
newbt=new binary_tree_node;
newbt->data=bt->data;

//travel bt and travel newbt at the same time
stack_left.push(bt);
stack_right.push(newbt);

while (!stack_left.empty())
{
pbinary_tree_node pleft=stack_left.top();
pbinary_tree_node pright=stack_right.top();
stack_left.pop();
stack_right.pop();
if (pleft->rchild!=0)
{
stack_left.push(pleft->rchild);
pright->rchild=new binary_tree_node;
pright->rchild->data=pleft->rchild->data;
stack_right.push(pright->rchild);
}
if (pleft->lchild!=0)
{
stack_left.push(pleft->lchild);
pright->lchild=new binary_tree_node;
pright->lchild->data=pleft->lchild->data;
stack_right.push(pright->lchild);
}
}
}
return newbt;
}

这个算法使用了两个栈，一个栈用来遍历原来的二叉树，另一个栈一边创建新的二叉树，一边同第一个栈同步，保存遍历时的轨迹。