See here for an example of an iterator: http://codereview.stackexchange.com/a/9399/507https://codereview.stackexchange.com/a/9399/507 (though I did not make the container as well as I could because I did not specify the types I should have).
See here for an example of a linked list using a single sentinel.
http://codereview.stackexchange.com/a/126007/507https://codereview.stackexchange.com/a/126007/507