creatree.c

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#include <stdio.h>
#define m 3
typedef char datatype;
typedef struct node {
     datatype data;
     struct node *child[m];
} node,*tree;
void createtree(tree *p)
 {/*按前序遍历顺序建立一棵3度树的递归算法*/
   
   int i; char ch;
   
   if ((ch=getchar())==' ')  *p=NULL;
   else
      {
	 *p=(tree) malloc (sizeof(node));
	 (*p)->data=ch;
	 for (i=0;i<m;++i)
	   createtree(&(*p)->child[i]);
      }
     
   }
void postorder(tree p)
 {/*树的后序遍历*/
    int i;
    if (p!=NULL)
     {
      
      for (i=0;i<m;++i)
	 postorder(p->child[i]);
      printf("%c",p->data);
      }
  }
 main()
 {
   tree t;
   printf("please input the preorder sequence of the tree:\n");
   createtree(&t);
   printf("\nthe postorderis:");
   postorder(t);
}