Linked list class with an Integer value per node
A node is made up of the following components:
- int content; <- used for storing a value
- Node *next; <- pointer to next List-Node
Following Methods are provided:
- Add <- Adds Item at the end of the list
- Remove <- Removes Node at given position
- Insert <- Inserts Node at the position of the given value or at the end
- Seek <- Looks up node with given value, returns adress or null-pointer
- Sum <- adds all the list node contents and reutrns the sum of them.