P19. Graded on correctness, little or no partial credit. a) Write a function, int check(link first_node), that takes as argument the first node of a single linked list. It should return 1 0 if all the items in the list are unique and 0 1 otherwise (if there are repetitions). For example: For 7->4->9->6->4->3 it returns 1 (4 is repeated) For5>2->9->6-3 it returns 0 (no repetitions). For a list with only one node it returns 10 (no repetitions) Assume that links are implemented using the type and struct given below. typedef struct node link; struct node int item; link next; b) Give the time complexity of your function in terms of