c++ linked list pointer segmentation fault -

i getting segmentation fault code below when program reaches addnode() function. don't know if there issues elsewhere since flow not going forward

#include<iostream> using namespace std; struct node {     int value;     node *next; }; node *head; void addnode(int); void destroytree(); int main() {     head=new node;     head=null;     int no,ch=1;     while(ch!=0)     {         cout<<"enter choice (0 exit, 1 enter): ";         cin>>ch;         if(ch==0) break;         cout<<"enter no: ";         cin>>no;         addnode(no);     }     cout<<"\ntime print.\n\n";     destroytree();     cout<<endl;     return 0; } void addnode(int no) {     node *n=new node;     node *trav;     trav=head;     while(trav!=null && trav->next!=null)     {         trav=trav->next;     }     if(trav==null)     {         trav->value=no;         trav->next=null;         return;     }     n->value=no;     n->next=null;     trav->next=n; } void destroytree() {     node *n;     while(head!=null)     {         n=head;         cout<<head->value<<"->next **   ";         head=head->next;         delete n;     } } 

classes not allowed. want 'head' point start of list in cases except destroytree(). add node end of list, start 'head' , move on till next null. destroy tree, print first element delete it. print next element , delete till node->next null

you dereferencing null pointer doesn't make sense. repeating in code below maybe you're not thinking through you're doing.

if(trav==null) {     trav->value=no;     trav->next=null;     return; } n->value=no; n->next=null; trav->next=n; 

apart assigning values node, you're looking drop new node end of list. if didn't find traversing list it's because list empty end of list head.

n->value=no; n->next=null; (trav != null ? trav->next : head) = n;