c++ use of *& as parameter (Pointer fun, tertiary tree method) - c++

Question

I'm trying to write a method which adds a key-value pair to a tertiary tree, but I'm obviously doing something wrong as I get a segfault whenever I reach the marked code
void Tree::add(int k, Node *&r)
{
cout<<"add"<<endl;
if(r==NULL){
r = new Node(k);
//check(heap area);
}
begin problem code
else if(r->keyCount == 1){
cout<<"adding second key";
if(r->getKey() < k){
Node * temp = new Node(r->getKey(),k,r->data[0],0);
delete r;
r = temp;
r->keyCount++;
cout<<"test"<<endl;
}
else
{
Node * temp = new Node(k,r->getKey(),0,r->data[0]);
delete r;
r = temp;
r->keyCount++;
cout<<"test"<<endl;
}
end code
}
else if(k < r->getKey())
{
cout<<"left"<<endl;
add(k,r->child[Node::L]);
}
else if(r->keyCount > 1 && k < r->getKey(1))
{
cout<<"middle"<<endl;
add(k,r->child[Node::M]);
}
else if(r->keyCount > 1 && k > r->getKey(1))
{
cout<<"right"<<endl;
add(k,r->child[Node::R]);
}
else
r = new Node(k);
}
What I'm trying to do is, in the case that there is only 1 out of the 2 keys used in this particular node, replace the current node with a new node which has the keys in the appropriate places (lesser val in key[0], greater val in key[1])
How do I do this properly?
My code apparently deletes both the address AND pointer for the old node, but doesn't properly reassign the pointer to the new node.
EDIT
updated code. the output is as follows:
% p4
Enter pairs consisting of an int and a double. I create a
ternary tree, keeping the data in order, by int. Finish entering
data by pressing ^d
2 2
add
Entering the pair: 2, 2
1 1
add
adding second key to current node
test
Entering the pair: 1, 1
-1 -1
add
left
add
Entering the pair: -1, -1
3 3
add
right
Segmentation Fault
EDIT 2
Here's a link to a zip containing the entire project if you want to look at all the code: http://sdrv.ms/WSrLfv
EDIT 3
More error data - output from gdb on crash
Program received signal SIGSEGV, Segmentation fault.
0x08051628 in getData (x=#0x8047554) at testTree.cc:26
26 x[k]=d;
Current language: auto; currently c++
EDIT 4
stepping through gdb to the segfault:
Breakpoint 1, Tree::add (this=0x8047554, k=3, r=#0x8047554) at tree.cc:58
58 cout<<"add"<<endl;
(gdb) n
add
61 if(r==NULL){
(gdb) n
65 else if(r->keyCount == 1){
(gdb) n
87 else if(k < r->getKey())
(gdb) n
92 else if(r->keyCount > 1 && k < r->getKey(1))
(gdb) n
97 else if(r->keyCount > 1 && k > r->getKey(1))
(gdb) n
99 cout<<"right"<<endl;
(gdb) n
right
100 add(k,r->child[Node::R]);
(gdb) n
Breakpoint 1, Tree::add (this=0x8047554, k=3, r=#0x806416c) at tree.cc:58
58 cout<<"add"<<endl;
(gdb) n
add
61 if(r==NULL){
(gdb) n
62 r = new Node(k);
(gdb) n
107 }
(gdb) n
107 }
(gdb) n
Tree::operator[] (this=0x8047554, index=3) at tree.cc:47
47 return *(locate(index,root)->data);
(gdb) n
48 }
(gdb) n
Program received signal SIGSEGV, Segmentation fault.
0x08051628 in getData (x=#0x8047554) at testTree.cc:26
26 x[k]=d;
(gdb)

Answer 1

This should be working.
In response to your edit: I noticed something interesting in your ouput:
-1 -1
add
left
add
Entering the pair: -1, -1
Notice how it says "left" and then it says "add" afterward because of the recursive call. However, in the input that crashes the program you don't see "add" after:
3 3
add
right
Segmentation Fault
If you look at your Tree::locate function:
Node * Tree::locate(int k, Node *rt) const
{
if(rt==NULL)
return rt;
if(k==rt->getKey())
return rt;
if(rt->keyCount>1 && k==rt->getKey(1))
return rt;
if(k < rt->getKey())
{
return locate(k,rt->child[Node::L]);
}
else if(rt->keyCount>1 && k < rt->getKey(1))
{
return locate(k,rt->child[Node::M]);
}
else if(rt->keyCount>1 && k<rt->getKey(1))
{
return locate(k,rt->child[Node::R]);
}
else
return NULL;
}
This line:
else if(rt->keyCount>1 && k<rt->getKey(1))
is the same condition as the previous one, so it is being skipped completely.