C/C++: how to clear a linked circular list
Submitted by Serguei_Tarassov on
In a linked circular list you need to add some checks to avoid memory corruption.
Full example (compiled OK with GCC 8.x)
#include <iostream> #include <cstdlib> struct Node { Node(Node* prev, int val) : prev(prev), next(NULL), value(val) { } Node *prev, *next; int value; }; void clear_list(Node*& head) { if (head != NULL) { Node* curr = head->next; while (curr != NULL && curr != head) { std::cout << "Deleting " << curr->value << std::endl; Node* temp = curr; curr = curr->next; delete temp; }; delete head; head = NULL; } } void print_list(Node*& head) { if (head != NULL) { Node* curr = head; do { std::cout << (curr == head ? "Head: " : "") << curr->value << std::endl; curr = curr->next; } while (curr != NULL && curr != head); } } int main() { Node* head = new Node(NULL, 0); Node* curr = head; for (int i = 1; i <= 10; i++) { Node* prev = curr; curr = new Node(prev, i); prev->next = curr; } // Link end to head curr->next = head; // print_list(head); clear_list(head); print_list(head); }
Result
Head: 0 1 2 3 4 5 6 7 8 9 10 Deleting 1 Deleting 2 Deleting 3 Deleting 4 Deleting 5 Deleting 6 Deleting 7 Deleting 8 Deleting 9 Deleting 10