Reverse LinkedList.java

//reverse singly linked list
public static Node reverseList(Node root){
    if(root == null) return null;
    return reverseListHelp(root);
}

public static Node reverseListHelp(Node root){
    if(root.next == null) return root;
    Node end = reverseListHelp(root.next);
    root.next.next = root;
    root.next = null;
    return end;
}