#include <stdio.h>
#include <stdlib.h>

typedef struct Node node;
struct Node {
  int collegeid;
  struct Node *next;
};

void insert(node **last, int collegeid) {
  node *dst = malloc(sizeof(node));
  dst->collegeid = collegeid;

  if (*last == NULL) {
    dst->next = dst;
    *last = dst;
  } else {
    dst->next = (*last)->next;
    (*last)->next = dst;
  }
}

void delete (node **last) {
  node *prev = NULL;

  if ((*last)->next == (*last))
    goto cleanup;

  prev = *last;
  while (prev->next != *last)
    prev = prev->next;

  prev->next = (*last)->next;

cleanup:
  free(*last);
  *last = prev;
}

void display(node *last) {
  node *cur = last;
  while (cur->next != last) {
    printf("%d ", cur->next->collegeid);
    cur = cur->next;
  }
  printf("%d\n", last->collegeid);
}

int main() {
  node *last = NULL;

  insert(&last, 1);
  insert(&last, 4);
  insert(&last, 99);
  insert(&last, 1223);
  display(last);

  delete (&last);
  display(last);

  // free
  while (last != NULL)
    delete (&last);
}