二叉树-----二叉链表-----遍历（7种）
//main.cpp#include "BTtree.h"int main(){ BTtree<char> tree; tree.pre_create(); tree.pre_order(tree.return_root()); cout << endl; tree.in_order(tree.return_root()); cout << endl; tree.post_order(tree.return_root()); cout << endl << endl; tree.nrec_pre_order(tree.return_root()); cout << endl; tree.nrec_in_order(tree.return_root()); cout << endl; tree.nrec_post_order(tree.return_root()); cout << endl << endl; tree.level_order(tree.return_root()); return 0;}//ABDH##I##E##CF#J##G##//ABDHIECFJG//HDIBEAFJCG//HIDEBJFGCA////ABDHIECFJG//HDIBEAFJCG//HIDEBJFGCA////ABCDEFGHIJ