Example - 1

The following example contains the method size that is used to determine the number of nodes in a linked list. The method is passed a pointer to the head of the linked list.

int data;struct node* next;
// // Returns the number of nodes in a linked list from// 
// // the given pointer to the head of the list.// 


tail = current;current = current->next;
struct node* current = head;struct node* tail;while (current != NULL) {}return tail - head;
// // other methods for manipulating the list// 
struct node {};int size(struct node* head) {}...

However, the method creates a pointer that points to the end of the list and uses pointer subtraction to determine the number of nodes in the list by subtracting the tail pointer from the head pointer. There no guarantee that the pointers exist in the same memory area, therefore using pointer subtraction in this way could return incorrect results and allow other unintended behavior. In this example a counter should be used to determine the number of nodes in the list, as shown in the following code.

count++;current = current->next;
struct node* current = head;int count = 0;while (current != NULL) {}return count;...int size(struct node* head) {}