能把一个带空位置的二叉树前序序列流转换成一棵二叉树,空位置用“@”表示,其中包含图形界面（java实现），可以帮助大家熟悉二叉树的存储结构，由前序序列流产生二叉树；二叉树的3种遍历算法-can take a position in the air before the sequence sequence binary tree circulation replaced by a binary tree. Air location with "@", which include