P19. Write all functions in C, use other language like C++ or Java will be no 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 10 if all the items in the list are unique and 0 1 otherwise (if there are repetitions). For example: or 7->4->9-6>4->3 it returns 1 (4 is repeated For 5->2->9->6->3 it returns 0 (no repetitions). For a list with only one node it returns 0 (no repetitions). Assume that links are implemented using the type and struct given below. typedef struct node link; struct node int item; link next l: b) Give the time complexity of your function in terms of o