Question

#include<iostream>
using namespace std;
/*main  idea  is to construct ordered statistic tree,which is  similar of
binary search tree,width addition of  one key,which shows us it's rank in given  
tree,for this i introduced additional one key-rank
*/
struct node
{
    int val;
    node *left,*right;
    int rank;
    node(int t) { val=t;left=right=NULL;}


};
node *root;
void insert(node *p,int ele)
{
    if(p==NULL){
        p=new node(ele);
        return ;


    }
    else if(ele<p->val)
    {
        insert(p->left,ele);

    }
    else if(ele>p->val)
    {
        insert(p->right,ele);

    }

}
void inorder (node *p)
{
    if(p!=NULL){ inorder(p->left);
    cout<<p->val<<" "<<p->rank;
    inorder(p->right);
    }

}
int count_node(node *t)
{
    int sum=0;
    if(t==NULL) return 0;
    else sum=1;
    if(t->left) sum+=count_node(t->left);
    if(t->right) sum+=count_node(t->right);
    return sum;
}

int main()
{
    root=NULL;
    root->rank=0;
    insert(root,26);
    insert(root,17);
    insert(root,41);
    insert(root,14);
    insert(root,30);
    insert(root,21);
    insert(root,47);
    insert(root,10);
    insert(root,16);
    insert(root,28);
    insert(root,38);
    insert(root,35);
    insert(root,39);
    insert(root,19);
    insert(root,21);
    insert(root,20);
    insert(root,7);
    insert(root,12);
    insert(root,3);
    inorder(root);

    return 0;
}

This code causes an overflow, but I do not understand why, because I have constructed the constructor properly.

Answer 1

The problem is:

root=NULL;
root->rank=0;

this cause undefined behavior because you dereference a NULL pointer. Anything can happen.

Also:

void insert(node *p,int ele)
{
    if(p==NULL){
        p=new node(ele);
        return ;


    }
    //...
}

This doesn’t modify the original pointer. If you call insert on a NULL pointer, it will be NULL when the function returns. You need to pass it by reference:

void insert(node *& p,int ele)