Does anyone see what is causing a segmentation fault in this BST code?

#include <iostream>

using namespace std;

#define YES 1
#define NO 0

class tree
{
    private:

    public:
        struct leaf
        {
            int data;
            leaf *l;
            leaf *r;
        };
        struct leaf *p;

        tree();
        ~tree();
        void destruct(leaf *q);
        tree(tree& a);
        void findparent(int n,int &found,leaf* &parent);
        void findfordel(int n,int &found,leaf *&parent,leaf* &x);
        void add(int n);
        void transverse();
        void in(leaf *q);
        void pre(leaf *q);
        void post(leaf *q);
        void del(int n);
        leaf*  createBST(int *preOrder, int* inOrder, int len);

};

tree::tree()
{
    p=NULL;
}

tree::~tree()
{
    destruct(p);
}

void tree::destruct(leaf *q)
{
    if(q!=NULL)
    {
        destruct(q->l);
        del(q->data);
        destruct(q->r);
    }
}
void tree::findparent(int n,int &found,leaf *&parent)
{
    leaf *q;
    found=NO;
    parent=NULL;

    if(p==NULL)
        return;

    q=p;
    while(q!=NULL)
    {
        if(q->data==n)
        {
            found=YES;
            return;
 开发者_高级运维       }
        if(q->data>n)
        {
            parent=q;
            q=q->l;
        }
        else
        {
            parent=q;
            q=q->r;
        }
    }
}

void tree::add(int n)
{
    int found;
    leaf *t,*parent;
    findparent(n,found,parent);
    if(found==YES)
        cout<<"\nSuch a Node Exists";
    else
    {
        t=new leaf;
        t->data=n;
        t->l=NULL;
        t->r=NULL;

        if(parent==NULL)
            p=t;
        else
            parent->data > n ? parent->l=t : parent->r=t;
    }
}

void tree::transverse()
{
    int c;
    cout<<"\n1.InOrder\n2.Preorder\n3.Postorder\nChoice: ";
    cin>>c;
    switch(c)
    {
        case 1:
            in(p);
            break;

        case 2:
            pre(p);
            break;

        case 3:
            post(p);
            break;
    }
}

void tree::in(leaf *q)
{
    if(q!=NULL)
    {
        in(q->l);
        cout<<"\t"<<q->data<<endl;
        in(q->r);
    }

}

void tree::pre(leaf *q)
{
    if(q!=NULL)
    {
        cout<<"\t"<<q->data<<endl;
        pre(q->l);
        pre(q->r);
    }

}

void tree::post(leaf *q)
{
    if(q!=NULL)
    {
        post(q->l);
        post(q->r);
        cout<<"\t"<<q->data<<endl;
    }

}

void tree::findfordel(int n,int &found,leaf *&parent,leaf *&x)
{
    leaf *q;
    found=0;
    parent=NULL;
    if(p==NULL)
        return;

    q=p;
    while(q!=NULL)
    {
        if(q->data==n)
        {
            found=1;
            x=q;
            return;
        }
        if(q->data>n)
        {
            parent=q;
            q=q->l;
        }
        else
        {
            parent=q;
            q=q->r;
        }
    }
}

void tree::del(int num)
{
    leaf *parent,*x,*xsucc;
    int found;

    // If EMPTY TREE
    if(p==NULL)
    {
        cout<<"\nTree is Empty";
        return;
    }
    parent=x=NULL;
    findfordel(num,found,parent,x);
    if(found==0)
    {
        cout<<"\nNode to be deleted NOT FOUND";
        return;
    }

    // If the node to be deleted has 2 leaves
    if(x->l != NULL && x->r != NULL)
    {
        parent=x;
        xsucc=x->r;

        while(xsucc->l != NULL)
        {
            parent=xsucc;
            xsucc=xsucc->l;
        }
        x->data=xsucc->data;
        x=xsucc;
    }

    // if the node to be deleted has no child
    if(x->l == NULL && x->r == NULL)
    {
        if(parent->r == x)
            parent->r=NULL;
        else
            parent->l=NULL;

        delete x;
        return;
    }

    // if node has only right leaf
    if(x->l == NULL && x->r != NULL )
    {
        if(parent->l == x)
            parent->l=x->r;
        else
            parent->r=x->r;

        delete x;
        return;
    }

    // if node to be deleted has only left child
    if(x->l != NULL && x->r == NULL)
    {
        if(parent->l == x)
            parent->l=x->l;
        else
            parent->r=x->l;

        delete x;
        return;
    }
}


tree::leaf* tree::createBST(int *preOrder, int* inOrder, int len)
{
    int i;
    tree::leaf *bst = new tree::leaf;
//  tree bst;
    if(len < 0)
        bst = NULL;
        return bst;

    bst->data = *preOrder;
    for(i = 0; i < len; i++)
        if(*(inOrder + i) == *preOrder)
        break;
    bst->l = createBST(preOrder + 1, inOrder, i);
    bst->r = createBST(preOrder + i +1, inOrder + i + 1, len-i-1);
    return bst;

}

int main()
{
/*  tree t;
    int data[]={32,16,34,1,87,13,7,18,14,19,23,24,41,5,53};
    for (int iter=0; iter<15; iter++)
    {
        t.add(data[iter]);
    }
    t.transverse();
    t.del(16);
    t.transverse();
    t.del(41);
    t.tranverse();
*/  

    tree bst;
    int pre_data[] = {20,8,4,12,10,14,22};
    int in_data[] = {4,8,10,12,14,20,22};
    bst.p = bst.createBST(pre_data, in_data, 7);
    bst.transverse();

    return 0;
}

***************Edited:***************************

Compile free error. But I got segmentation fault after run.

Run it under gcc.

---

tree::leaf* tree::createBST(int *preOrder, int* inOrder, int len)
{
    int i;
    tree::leaf *bst = new tree::leaf;
    //  tree bst;
    if(len < 0)
        bst = NULL;
    return bst;  // This doesn't come under `if` statement. Nothing gets executed 
                 // after this statement. So, returning a leaf whose members are 
                 // not initialized at all.

    // ....

}

Now you are collecting it main() -

bst.p = bst.createBST(pre_data, in_data, 7);

The members of bst.p( i.e., l,r, data ), are not assigned any values. But you are requesting for any of those on call to in(..), pre(..), post(..) and hence the segmentation fault.

---

As Mahesh's comment hints, your createBST method doesn't actually modify the tree object you call it on. So your tree starts off empty; it isn't made nonempty by calling createBST; your traversal of the tree then does nothing because you're traversing an empty tree.