Linked List: common mistakes

One wrong pointer and part of the list is gone, or the list loops for ever. Here are three slips: Reverse Linked List moving along the link it just flipped, forgetting head.next = null, and Middle of the Linked List checking only fast.next.

Pick a mistake and press play: Wrong runs the code with the mistake until it breaks, and the code marks the wrong line in red. Fixed runs the corrected code on the same input, with the corrected line in green.