#include <iostream> #include <cstdio> #include <math.h> using namespace std; struct list { int item; list *next; public: list() {} list(int val, list *Next) : item(val), next(Next) {} }*head = NULL; list *lastItem(list *head) { if (head == NULL) return 0; else { while (head->next != NULL) head = head->next; } return head; } void pushBeginning(list **head, int data) { *head = new list(data, *head); } void pushEnd(list **head, int number) { if (*head == NULL) { *head = new list(number, *head); } else { list *last = lastItem(*head); last->next = new list(number, last->next); } } void delStart(list *head) { list *tmp = head->next; list *current = head; delete current; head = tmp; } void delEnd(list *head) { list *last = lastItem(head); list *tmp = head; while (tmp->next != last) tmp = tmp->next; tmp->next = last->next; delete(last); head = tmp; } void show(list *head) { if (head) { cout << head->item << ' '; show(head->next); } else cout << '\n'; } int main() { //head = new list(); //list *head = NULL; pushBeginning(&head, 1); pushEnd(&head, 1000); pushEnd(&head, 1); pushEnd(&head, 15); pushEnd(&head, 150); show(head); delEnd(head); show(head); delStart(head); show(head); return 0; }

Closed due to the fact that off-topic participants are free_ze , pavel , Kromster , Streletz , aleksandr barakin 2 Sep '16 at 6:30 .

It seems that this question does not correspond to the subject of the site. Those who voted to close it indicated the following reason:

  • “Questions asking for help with debugging (“ why does this code not work? ”) Should include the desired behavior, a specific problem or error, and a minimum code for playing it right in the question . Questions without an explicit description of the problem are useless for other visitors. See How to create minimal, self-sufficient and reproducible example . " - pavel, Kromster
If the question can be reformulated according to the rules set out in the certificate , edit it .

  • and the minimum example is possible? At first glance, there is no problem. Apart from what is assigned to a local variable. Why in functions to block head local global? - pavel
  • I do everything according to the book, in the book an example was added with an addition to the beginning, I am trying to do more functionality, but show (head) does not display as it should - Ilya
  • let's say, in delStart or pass a list **head or don’t transmit anything at all. - pavel
  • I made the show () function without parameters, why is it displayed once? - Ilya
  • because you for some reason made it recursive. It cannot do without a parameter (leaving a recursion), but call it then not head but somehow for example current - pavel

1 answer 1

because function

 void delStart(list *head) { list *tmp = head->next; list *current = head; delete current; head = tmp; }

accepts a pointer that remains to be pointed to where it is and pointed to before the call, since the address of the pointer is copied to the function, the original does not change. You need to pass a pointer to a pointer, that is:

 void delStart(list **head) { list *tmp = *head->next; list *current = *head; delete current; *head = tmp; }