Given a sorted linked list, remove all the duplicates from the list. For example, given 1->2->3->3->6, return 1->2->6. Another example, given 1->1->1->2->4, return 2->4.

typedef struct node Node; /* The function removes duplicates from a sorted list */ void removeDuplicates(Node** head) { /* do nothing if the list is empty */ Node* current = *head; if(current == NULL) return; /* Pointer to traverse the linked list */ Node* pre_head = (Node*) malloc(sizeof(Node)); pre_head->next = *head; /* Pointer to store the next pointer of a node to be deleted*/ Node* next_next; Node* pre = pre_head; bool deleted = false; /* Traverse the list till last node */ while(current->next != NULL) { /* Compare current node with next node */ if(current->data == current->next->data) { /*The sequence of steps is important*/ next_next = current->next->next; free(current->next); current->next = next_next; deleted = true; } else if (deleted) { pre->next = current->next; free(current); current = pre->next; deleted = false; } else { pre = current; current = current->next; } } /* remove the last duplicated node*/ if (deleted) { pre->next = NULL; free(current); } *head = pre_head->next; free(pre_head); }

To test the code, please use the testing program from http://www.geeksforgeeks.org/remove-duplicates-from-a-sorted-linked-list/.