using this struct:
typedef struct node {
int content;
struct node* right;
struct node* left;
}Node;
I'm trying to write a code that return the pointer of the the node if node ->content== x I have tried this so far but I don't think its right:
Node* find (Node* p,int x)
{
Node* L,*R;
if(p==NULL)
retutn NULL;
L=find(p->left,x);
if(L->content == x)
return L;
R=find(p->right,x);
if(R->content == x)
return R;
}
can u help me correct my code?
First, the code doesn't even compile because of retutn
.
L=(p->left,x); // Equivalent to: L = x;
should be
L=find(p->left,x);
Same idea for the right side.
L
could be NULL.
if(L->content == x)
should be
if(L != NULL)
or just
if(L)
Same idea for the right side.
You never check if the current node is a match. You need to add the following:
if ( p->content == x )
return p;
The following is correct:
Node* L, *R;
However, it's very easy to accidentally do
Node* L, R;
Maybe you should avoid grouping such declarations. On the plus side, this should be caught at compile-time (unless you avoid turning on even the most basic warnings).
All together,
Node* find(Node* p, int x)
{
if ( !p )
return NULL;
if ( p->content == x )
return p;
Node* L = find( p->left, x );
if ( L )
return L;
Node* R = find( p->right, x );
if ( R )
return R;
return NULL;
}
The part of the function starting from these statements
L=find(p->left,x);
if(L->content == x)
return L;
is incorrect. For starters it is unclear why the node pointed to by the pointer p is not checked. And the call of the function can return a null pointer. So this if statement can invoke undefined behavior.
The function definition depends on whether it is a binary search tree or not. That is whether nodes of the tree are ordered.
If it is not a binary search tree then the function can be defined the following way
Node * find( const Node *root, int x )
{
if ( root == NULL )
{
return NULL;
}
else if ( root->content == x )
{
return ( Node * )root;
}
else
{
Node *p = find( root->left, x );
p == NULL ? return find( root->right, x ) : p;
}
}
If the tree is a binary search tree then the function can look the following way
Node * find( const Node *root, int x )
{
if ( root == NULL )
{
return NULL;
}
else if ( x < root->content )
{
return find( root->left, x );
}
else if ( root->content < x )
{
return find( root->right, x );
}
else
{
return ( Node * )root;
}
}
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