#include<stdio.h>
typedef struct node{
  int child;
  struct node *next;
 }Child;
typedef struct pnode{
 char data;
 Child *headptr;
 }Pnode;
searchnode(Pnode h[],int n,char ch)
 {
  int i;
  for(i=0;i<n;i++)
   if(h[i].data==ch)return i;
  return -1;
 }
main()
{
 int n,i,j,k;char *s;Pnode *h; Child *p;
 printf("node number in tree:\n");
 do{
 scanf("%d",&n);}
 while(n<=0);
 getchar();
 h=(Pnode *)malloc(sizeof(Pnode)*n);
 printf("input each node:\n");
 gets(s);
 for(i=0;i<n;i++)
  {
   h[i].data=s[i];
   h[i].headptr=NULL;
  }
printf("input the relation between nodes:\n");
  for(i=1;i<=n-1;i++)
  {
   printf("input format:a->b:\n");
   gets(s);
   if((j=searchnode(h,n,s[0]))>-1 &&(k=searchnode(h,n,s[3]))>-1){
     p=(Child *)malloc(sizeof(Child));
     p->child=k;
     p->next=h[j].headptr;
     h[j].headptr=p;
     }
   }
 printf("input any node:\n");
 scanf("%d",&i);
 if(i>=0 && i<=n){
  for(k=0;k<n;k++)              /*查找孩子結點i的父結點k*/
    { 
     p=h[k].headptr;
     while(p){
     if(p->child==i)break;
      p=p->next;
     }
   if(p->child==i)break;
    }
  printf("parent node of %c is %c.\n",h[i].data,h[k].data);
  
  printf("the subnodes of %c are follows:\n",h[i].data);
  p=h[i].headptr;
  while(p){
   printf("%c ",h[p->child].data);
   p=p->next;
   }
 }
}