exp 2,4: init

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

4.c

@@ -0,0 +1,70 @@
+#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)
+    *last = dst;
+
+  if ((*last)->next == NULL)
+    (*last)->next = dst, dst->next = *last;
+  else {
+    dst->next = (*last)->next;
+    (*last)->next = dst;
+  }
+}
+
+void delete (node **last) {
+  node *prev = NULL;
+
+  if ((*last)->next == NULL)
+    goto cleanup;
+
+  prev = *last;
+
+  while (prev->next != *last)
+    prev = prev->next;
+
+  if (prev->next->next == prev)
+    prev->next = NULL;
+  else
+    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);
+}