c语言编程之二叉树

　　利用链表建立二叉树，完成前序遍历、中序遍历、后序遍历。

　　建立二叉树用的是前序遍历建立二叉树：

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

   typedef int element;
   typedef struct Tree{
           struct Tree *lchild,*rchild;
          char data;
  }*pTree,pNode;

  //char str[]="ABD#E##FG###CI##H##";
  char str[]="ABDH#K###E##CFI###G#J##";
  element index=;
  //Init a empty tree
  element Init_tree(pTree *T)
          {
             *T=NULL;
             printf("init a empty tree\n");
          }

  //build a tree
  void Creat_tree(pNode **T)
          {
             char num;
             num=str[index++];
             pTree P=NULL;
             //P=*T;
             if(num=='#')
                  *T=NULL;
             else
               {
                // if(!(*T))
                  // exit(OVERFLOW);
                 (*T)=(pTree)malloc(sizeof(pNode));
                 //memset(*T,0,sizeof(pNode));
                 (*T)->data=num;
                 Creat_tree(&(*T)->lchild);
                 Creat_tree(&(*T)->rchild);
               }
          }

  //pro order traversal
  element Pro_trav(pTree T)
          {
             if(T==NULL)
                  return ;
             printf("pro order traversal data:%c\n",T->data);
             Pro_trav(T->lchild);
             Pro_trav(T->rchild);
          }

  //midle order traversal
  element Mid_trav(pTree T)
          {
             if(T==NULL)
                  return;
             Mid_trav(T->lchild);
             printf("mid order traversal data:%c\n",T->data);
             Mid_trav(T->rchild);
          }

  //after traversal
  element Aft_trav(pTree T)
          {
             if(T==NULL)
                  return;
             Aft_trav(T->lchild);
             Aft_trav(T->rchild);
             printf("after order traversal data:%c\n",T->data);
          }

  element main()
          {
             pTree T;
             T=(pTree)malloc(sizeof(struct Tree));
             //Init_tree(&T);
             printf("before is ok\n");
             Creat_tree(&T);
             Pro_trav(T);
             Mid_trav(T);
             Aft_trav(T);
             return ;
          }
  

　　 输出结果：

 before is ok
 pro order traversal data:A
 pro order traversal data:B
 pro order traversal data:D
 pro order traversal data:H
 pro order traversal data:K
 pro order traversal data:E
 pro order traversal data:C
 pro order traversal data:F
 pro order traversal data:I
 pro order traversal data:G
 pro order traversal data:J
 mid order traversal data:H
 mid order traversal data:K
 mid order traversal data:D
 mid order traversal data:B
 mid order traversal data:E
 mid order traversal data:A
 mid order traversal data:I
 mid order traversal data:F
 mid order traversal data:C
 mid order traversal data:G
 mid order traversal data:J
 after order traversal data:K
 after order traversal data:H
 after order traversal data:D
 after order traversal data:E
 after order traversal data:B
 after order traversal data:I
 after order traversal data:F
 after order traversal data:J
 after order traversal data:G
 after order traversal data:C
 after order traversal data:A