CS460
Computer Controlled Railroad
with Multiple Cars
Erik Riggenbach
Computer Science Major
Senior at St Norbert College

Detecting Uncoupled Cars

I make a pretty large assumption about the size of the cars for this algorithm. They can not be long enough to cover more than one cell at a time. If they were, this would be a much greater problem.

My idea on this one is simply to check the count on the cells. I start with the photocell the train just hit and move backward following the track layout data structures. Essentially I use the track data structure as a linked list to traverse the track. I check if the cell is allocated to the train. If it is, I check what it's count is. If I get three cells in a row with the same count, I have a decoupled car. Another condition that tells if a car is uncoupled is having 2 cells with the same count and the one preceding those two has a count one or more greater.

Having two cells in a row with the same count does not indicate an uncoupled car. I do not de-allocate a cell until the cell after it has been passed over by the train as well. This means that for a small time (however long it takes for the last car to pass over the cell) two cells have the same count.