exp 2,4: init

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

2.c

@@ -0,0 +1,93 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Student student;
+struct Student {
+  int sid;
+  struct Student *next;
+};
+
+void insert(student **head, int idx, uint sid) {
+  student *new = malloc(sizeof(student));
+  new->sid = sid;
+
+  int i = 0;
+
+  student *prev = NULL, *cur = *head;
+
+  for (int i = 0;; i++) {
+    if (i == idx) {
+      if (prev != NULL)
+        prev->next = new;
+      else
+        *head = new;
+      new->next = cur;
+      return;
+    }
+
+    if (cur == NULL)
+      return;
+
+    prev = cur;
+    cur = cur->next;
+  }
+
+  printf("Index %d does not exist\n", idx);
+  return;
+}
+
+void delete (student **head, int idx) {
+  student *prev = NULL, *cur = *head;
+
+  for (int i = 0; cur != NULL; i++) {
+    if (i == idx) {
+      if (prev != NULL)
+        prev->next = cur->next;
+      else
+        *head = cur->next;
+      free(cur);
+      return;
+    }
+    prev = cur;
+    cur = cur->next;
+  }
+
+  printf("Index %d does not exist\n", idx);
+  return;
+}
+
+void reverse(student **head) {
+  student *prev = NULL, *cur = *head;
+
+  while (cur->next != NULL) {
+    student *next = cur->next;
+    cur->next = prev;
+    prev = cur;
+    cur = next;
+  }
+
+  cur->next = prev;
+
+  *head = cur;
+  return;
+}
+
+int main() {
+  student *head = NULL;
+  insert(&head, 0, 1);
+  insert(&head, 1, 2002);
+  insert(&head, 2, -9);
+  insert(&head, 3, 52);
+  insert(&head, 1, 4);
+  delete (&head, 2);
+  reverse(&head);
+
+  while (head != NULL) {
+    printf("%d ", head->sid);
+    head = head->next;
+  }
+
+  // free
+  while (head != NULL)
+    delete(&head, 0);
+}