Adding double linked circular list

lab12/double.c

@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct _dclist * List;
+
+struct _dclist {
+    int data;
+    List next;
+    List prev;
+};
+
+List init() {
+    List initializer = malloc(sizeof(struct _dclist));
+    initializer->data = 0;
+    initializer->next = initializer;
+    initializer->prev = initializer;
+    return initializer;
+}
+
+void insert(int data, List list) {
+    List head = list;
+    while ( list->next != head ) { // if we have next, go to it.
+        list = list->next;
+    }
+    list->next = malloc(sizeof(struct _dclist));
+    head->prev = list->next;
+    list->next->prev = list; // set the preview value;
+    list->next->data = data;
+    list->next->next = head;
+}
+
+void print(List list) {
+    List head = list;
+    while ( list->next != head) {
+        list = list->next;
+        printf("PREVIOUS VALUE: %d\n", list->prev->data);
+        printf("CURRENT VALUE: %d\n", list->data);
+    }
+    printf("Is it circular? %d means yes\n", list->next->data);
+}
+
+int main(void) {
+    List test = init();
+    insert(10, test);
+    insert(12, test);
+    insert(13, test);
+    insert(14, test);
+    insert(15, test);
+    print(test);
+    return 0;
+}