C++ Link list insert swop -

i want insert 2 4 , 4 2. getting errors swop. how fix code below swop.

#include <iostream>  struct nodetype {     int info ;     nodetype* link ; };  int main() {     nodetype* ptr ;     nodetype* list ;      ptr = new nodetype;     ptr->info = 1;     list = new nodetype;     ptr->info = 2;     list->link = ptr;     ptr = new nodetype;     ptr->info = 3;     ptr = new nodetype;     list->info = 4;     ptr->link = null;     list->link->link->link = ptr;      unsigned count = 1 ;     ptr = list ;     while ( ptr )     {         std::cout << "node #" << count++ << ':' << ptr->info << '\n' ;         ptr = ptr->link ;     } } 

i have tried various ways swop occur , getting compiler errors. thanks

nodetype* ptr ; nodetype* list ;  ptr = new nodetype; ptr->info = 1; 

the pointer ptr points node contains 1.

list = new nodetype; ptr->info = 2; 

now list points node, , node ptr points contains 2.

list->link = ptr; 

now 1 node connected other.

ptr = new nodetype; ptr->info = 3; 

now ptr points node, containing 3.

ptr = new nodetype; 

now ptr points another node, , node containing 3 has been lost.

list->info = 4; 

now first node in list contains 4.

ptr->link = null; 

all right.

list->link->link->link = ptr; 

now trying iterate past end of list (which has 2 nodes). dereference invalid pointer, causes undefined behavior; you're lucky if access violation error.

you must study pointers more before attempt swap in middle of list.