SinglyLinkedListNode* reverse(SinglyLinkedListNode* llist) {
    
    SinglyLinkedListNode* temp=llist,*curr=llist->next,*prev=NULL;
    while(temp->next!=NULL){
    temp->next=prev;
        prev=temp;
        temp=curr;
        curr=curr->next;
    }
    temp->next=prev;
    llist=temp;
    return llist;           
}