// Solution 2: Using recursive
ListNode* reverseList(ListNode* head) {
if (head == nullptr || head->next == nullptr) return head;
std::function<ListNode*(ListNode*, ListNode*)> reverseHelper = [&](ListNode *curr, ListNode *prev) -> ListNode*
{
if (curr == nullptr) return prev;
ListNode *next = curr->next;
curr->next = prev;
prev = curr;
return reverseHelper(next, prev);
};
return reverseHelper(head, nullptr);
}
// Performs recursive step of reverse process
Value *reverseHelper(Value *list, Value *newlist) {
assert(isNull(list) || list->type == CONS_TYPE);
if (isNull(list)) {
return newlist;
} else {
newlist = cons(copy_Value(car(list)), newlist);
return reverseHelper(cdr(list), newlist);
}
}
// Return a new list that is the reverse of the one that is passed in.
Value *reverse(Value *list){
Value *newlist = makeNull();
newlist = reverseHelper(list, newlist);
return newlist;
}