I think my code is right. It's pretty straight forward. Can any one
who solved this look at it?
--------------------------code------------------------------------

int main(void)
{
  int n,code[SIZE];
  int *m[SIZE],c[SIZE];
  int f[SIZE];
  int i,j,k;
  n=h=0;
  while(scanf("%d",&code[n])==1)
    code[n++]--;
  for(i=0;i<=n;i++){
    f[i]=c[i]=0;
    m[i]=(int *)malloc((1+f[i])*sizeof(int));
  }
  for(k=0;k<n;k++) f[code[k]]++;
  for(i=0;i<=n;i++)
    if(f[i]==0)
      HeapInsert(i);
  for(k=0;k<n;k++){
    i=code[k];
    j=ExtractMin();
    m[i][c[i]++]=j;
    m[j][c[j]++]=i;
    f[i]--;
    if(f[i]==0)
      HeapInsert(i);
  }
  for(i=0;i<=n;i++){
    printf("%d:",i+1);
    qsort(m[i],c[i],sizeof(int),comp);
    for(j=0;j<c[i];j++)
      printf(" %d",m[i][j]+1);
    printf("\n");
  }
  return 0;
}