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Deleting Within A Tree

Posted on 1998-06-25
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Last Modified: 2010-04-01
Need help with code that will enable the user to delete a node within a tree of words.
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Question by:John500
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nietod earned 160 total points
ID: 1166653
I assume this if for me.  right?  If you send me a final copy.  (If we are there yet.)  I'll paste it in here.
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LVL 22

Expert Comment

by:nietod
ID: 1166654
The final code:
*********************
void Probe::hook(Node *ptr,BinTree *tree, Node *par, Node *cur)
{
 if(_top == 0)
 {
  tree->_root = ptr;
 }
 else if(cur == par->_left)
 {
  par->_left = ptr;
 }
 else
 {
  par->_right = ptr;
 }
 _trail[_top] = ptr;
}

void Probe::deleteCurrent(BinTree *tree)
{ // delete current node: trail [top]
 if(_top < 0)
  return;  // empty tree

 Node *par, *cur = _trail[_top];  // nicer name for current node

 tree->_numNodes--;  // adjust tree statistics
 tree->_numWords -= cur->_count;

 if(_top > 0)
  par = _trail[_top - 1];  //parent if current node has one

 if(!cur -> _left) // has no left child, might have right child
 {
  hook(cur->_right,tree,par,cur);
  if(!_trail[_top]) _top--;  // node gone, back up
 }

 else if (!cur->_right)  // has no right child, does have left child
 {
  hook(cur->_left,tree,par,cur);
 }

 else  // cur has both children present
 {
  // find inorder successor to cur
  Node * p = cur->_right;
  if(!p->_left)  // already at inorder successor
  {
   p->_left = cur->_left;  // make p's left ptr same as cur's
   hook(p,tree,par,cur);
  }
  else
  {
   while(p->_left && p->_left->_left)
   { p = p->_left;
    // now p points to parent of inorder successor to cur
    Node *succ = p->_left;
    p->_left = succ->_right;  // hook up subtree

    succ->_left = cur->_left;
    succ->_right = cur->_right;
    hook(succ,tree,par,cur);
   }
  }
 }
 cur->_left = NULL;
 cur->_right = NULL;
 delete cur;
}

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Author Comment

by:John500
ID: 1166655
Much Thanks!
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