iterative algorithm for pre-order traversal

This is done by an algormthm called Morris traversal.

void MorrisTraversal(struct Node *root)
 {  struct Node *p,*pre;

 if(root==0) { return; }

 for(p=root;p!=0;)
  {
  if(p->Left==0) { printf(" %d ",p->Data); p=p->Right; continue; }

  for(pre=p->Left;pre->Right!=0 && pre->Right!=p;pre=pre->Right) { }

  if(pre->Right==0)
   { pre->Right=p; p=p->Left; continue; }
  else
   { pre->Right=0; printf(" %d ",p->Data); p=p->Right; continue; }

  
  }
 }

}