二叉树的遍历

#include <stdio.h>
#include <stdlib.h>
typedef struct tree_node
{
 char data;
 struct tree_node *lchild,*rchild;
}BT_Node;
BT_Node *tree;
BT_Node * Creat_BTree(BT_Node *tree)
{
 char ch;
 ch=getchar();
 if(ch == '*')
 {
  tree=NULL;
 }
    else
 {
  tree=(BT_Node*)malloc(sizeof(BT_Node));
  tree->data=ch;
  tree->lchild=Creat_BTree(tree->lchild);
  tree->rchild=Creat_BTree(tree->rchild);
 }
 return tree;
}
void Visit_Node(BT_Node *tree)
{
 printf(" ");
 putchar(tree->data);
 printf("\t");
}
void Pre_Order(BT_Node *tree)
{
 if(!tree)
 {
  return ;
 }
 else
 {
  Visit_Node(tree);
  Pre_Order(tree->lchild);
  Pre_Order(tree->rchild);
 }
}
void Mid_Order(BT_Node *tree)
{
 if(!tree)
 {
  return ;
 }
 else
 {
  Mid_Order(tree->lchild);
  Visit_Node(tree);
  Mid_Order(tree->rchild);
 }
}
void After_Order(BT_Node *tree)
{
 if(!tree)
 {
  return ;
 }
 else
 {
  After_Order(tree->lchild);
  Visit_Node(tree);
  After_Order(tree->rchild);
 }
}
int main(void)
{
 printf("请输入树结点:\n");
 tree=Creat_BTree(tree);
 if(tree)
 {
  printf("\n前序遍历:\n");
  Pre_Order(tree);
  printf("\n");
  printf("\n中序遍历:\n");
  Mid_Order(tree);
  printf("\n");
  printf("\n后序遍历:\n");
  After_Order(tree);
  printf("\n");
 }
 return 0;
}