public void deleteByMerging(int el)
{
IntBSTNode tmp,node,p=root,prev=null;
/*find the node to be deleted*/
while(p!=null&&p.key!=el)
{
prev=p;
if(p.key<el)
p=p.right;
else p=p.left;
}
/*find end*/
node=p;
if(p!=null&&p.key==el)
{
if(node.right==null)
//node has no right child then its left child (if any) is attached to 
node=node.left;
//its parent
  else if(node.left==null)
  //node has no left child then its right child (if any) is attched to
  node=node.right
  //its parent
else{
tmp=node.left;  
while(tmp.right!=null)
tmp=tmp.right;
//find the rightmost node of the left subtree
tem.right=node.right;
//establish the link between the rightmost node of the left subtree and the right subtree
node=node.left;
}
if(p==root)
{
root=node;
}
else if (prev.left==p)
{
prev.left=node;
}
else prev.right=node
}
else if(root!=null)
  {
System.out.println("the node is not in the tree");
}
else System.out.println("The tree is empty");
}