自己对这一块的知识掌握的不是很好，所以就整理了一下，下面是代码；


 

#include<stdio.h>
#include<malloc.h>

typedef struct tree_node
{
  char data;
  struct tree_node *lchild,*rchild;
}BT_node;

BT_node *tree;


//树的创建
BT_node *creat_tree(BT_node *tree)
{
  char c;
  c = getchar();

  if(c == '*')
  {
    tree = NULL;
  }
  else
  {
    tree = (struct tree_node *)malloc(sizeof(struct tree_node));
    tree->data = c;
    tree->lchild = creat_tree(tree->lchild);
    tree->rchild = creat_tree(tree->rchild);
  }
  return(tree);
}

//遍历根节点
void visit_node(BT_node *tree)
{
  printf(" ");
  putchar(tree->data);
  printf("\t");
}


//前序遍历
void pre_tree(BT_node *tree)
{
  if(!tree)
  {
    return;
  }
  else
  {
    visit_node(tree);
    pre_tree(tree->lchild);
    pre_tree(tree->rchild);
  }
}

//中序遍历
void mid_tree(BT_node *tree)
{
  if(!tree)
  {
    return;
  }
  else
  {
    mid_tree(tree->lchild);
    visit_node(tree);
    mid_tree(tree->rchild);
  }
}

//后序遍历
void after_tree(BT_node *tree)
{
  if(!tree)
  {
    return;
  }
  else
  { 
    after_tree(tree->lchild);
    after_tree(tree->rchild);
    visit_node(tree);
  }
}


int main()
{
  printf("请输入树节点...\n");
  tree = creat_tree(tree);

  if(tree)
  {
    printf("前序遍历\n");
    pre_tree(tree);
    printf("\n");

    printf("中序遍历\n");
    mid_tree(tree);
    printf("\n");

    printf("后序遍历\n");
    after_tree(tree);
    printf("\n");
  }
  printf("\n");
  return 0;
}