exp 3,5,6,7: init

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

7.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Node node;
+struct Node {
+  int id;
+  struct Node *next;
+};
+
+typedef struct Queue queue;
+struct Queue {
+  node *head;
+  node *tail;
+};
+
+int peek(queue *q) { return q->head->id; }
+
+void insert(queue *q, int id) {
+  node *new = malloc(sizeof(node));
+  new->id = id;
+  new->next = NULL;
+
+  if (q->tail)
+    q->tail->next = new;
+  else
+    q->head = new;
+
+  q->tail = new;
+}
+
+void delete (queue *q) {
+  if (!q->head)
+    return;
+
+  node *next = q->head->next;
+
+  free(q->head);
+
+  q->head = next;
+
+  if (!q->head)
+    q->tail = NULL;
+}
+
+void display(queue *q) {
+  node *cur = q->head;
+  while (cur != NULL) {
+    printf("%d ", cur->id);
+    cur = cur->next;
+  }
+  printf("\n");
+}
+
+int main() {
+  queue *q = malloc(sizeof(queue));
+  insert(q, 56);
+  insert(q, 3);
+  insert(q, 99);
+  delete(q);
+  display(q);
+
+  // free
+  while (q->head != NULL)
+    delete(q);
+  free(q);
+}