数据结构----5、二叉树的建立与前中后序遍历，代码简单易懂

#include<bits/stdc++.h>
using namespace std;
#define status char
typedef struct tree{
  status data;
  struct tree *lchild;
  struct tree *rchild;
}tree,*btree;
void CreatTree(btree & tr)
{
 status ch;
 cin>>ch;
 if(ch=='#')
 {
  tr=NULL ; 
 }
 else{
 tr=new tree;
 tr->data=ch;
 CreatTree(tr->lchild);
 CreatTree(tr->rchild); 
 }
 return ;
}
int TreeCount(btree & tr)
{
 if(tr==NULL)
  return 0;
 else 
  return TreeCount(tr->rchild)+TreeCount(tr->lchild)+1; 
}
void PreOrderTree(tree * tr)
{
 if(tr==NULL)
 {
  return ;
 }
 cout<<tr->data<<" ";
 PreOrderTree(tr->lchild);
 PreOrderTree(tr->rchild);//cout<<"1";
 
}
void InOrderTree(tree * tr)
{
 if(tr==NULL)
 {
  return ;
 }
 InOrderTree(tr->lchild);
 cout<<tr->data<<" ";
 InOrderTree(tr->rchild);
}
void PostOrderTree(tree * tr)
{
 if(tr==NULL)
 {
  return ;
 }
 PostOrderTree(tr->lchild);
 PostOrderTree(tr->rchild);
 cout<<tr->data<<" ";
}
void menu()
{
 cout<<"1、初始化二叉树"<<endl<<"2、先序遍历二叉树"<<endl<<"3、中序遍历二叉树"<<endl<<"4、后序遍历二叉树"<<endl<<"5、树的总节点个数"<<endl<<"6、退出程序"<<endl; 
}
int main()
{
 tree *tre;
 menu();
 while(1)
 {
 int n;
 cin>>n;
 switch(n)
 {
  case 1:
   CreatTree(tre);
   break;
  case 2:
      PreOrderTree(tre);
      cout<<endl;
   break;
  case 3:
      InOrderTree(tre);
      cout<<endl;
   break;
  case 4:
      PostOrderTree(tre);
      cout<<endl;
   break;
  case 5:
      cout<<TreeCount(tre)<<endl;
      break;
  case 6:
   exit(0);
         
  } 
  } 
 return 0;
 }