What are C ++ self-relational types for?

Question

What are the use cases for self-referencing types?

With the help of self-relational types, I mean:

class T { T *ptr; // member variable that references the type of the class }; 

Answer 1

This is one of the most effective ways to create linked lists or the Hierarchy tree.

 #include <iostream> class linked_ints { public: linked_ints() : next(nullptr), x(0) {} linked_ints* next; int x; }; void print(linked_ints* b) { if(b == nullptr) return; do { std::cout << b->x << std::endl; } while((b = b->next)); } int main() { linked_ints x, y, z; x.next = &y; y.next = &z; print(&x); return 0; } 

Answer 2

One example that I can think of is linked lists .

An example taken from here :

 #include<iostream> struct Node{ int data; Node* next; }; void InsertAfter(Node **head, int value){ if(*head==NULL){ Node* temp=NULL; temp = new Node; temp->data = value; temp->next = NULL; *head = temp; }else{ Node *temp = new Node; temp->data = value; temp->next = (*head)->next; (*head)->next = temp; } } void DeleteAfter(Node **head){ if(*head==NULL){ return; }else{ Node *temp = NULL; temp = (*head)->next; (*head)->next = (*head)->next->next; delete temp; temp=NULL; } } int DeleteAll(Node **head,int value){ int count=0; Node *p = NULL; Node *q = (*head); if(*head==NULL){ count =0; }else{ while((q)!=NULL){ if((q)->data==value){ Node *temp = NULL; temp = q; if ( p!=NULL){ p->next = q->next; }else{ (*head) = q->next; } q = q->next; delete temp; temp = NULL; ++count; }else{ p = q; q = q->next; } } } return count; } void DisplayList(Node *head){ if(head!=NULL){ std::cout << head->data << "\n"; while(head->next!=NULL){ std::cout << head->data << "\n"; head = head->next; } std::cout << "\n\n"; } int main(){ Node *head=NULL; InsertAfter(&head,10); InsertAfter(&head,10); InsertAfter(&head,20); InsertAfter(&head,10); DisplayList(head); DeleteAfter(&head); DisplayList(head); int a = DeleteAll(&head,10); std::cout << "Number Of Nodes deleted having value 10 = " << a <<"\n\n"; DisplayList(head); return 0; }