description.txt

Each day is divided into 2 separate shifts of 12 hours (day/night).

There are a number of required nurses for each of them. 

A nurse is off on a specific day if no shift is assigned or if the nurse has requested a PTO on that specific day. 

The planning length is 4 weeks (28 days). 

Each nurse should work either 12, 24 or 36 hours hours per week.

* No nurse will work on both shifts in the single day.
* A nurse who works on today's night will not work on next day.


The problem can be decomposed into three independent stages.

1. Check there are enough nurses to provide adequate cover. 
2. The second stage assigns the nurses to the correct number of day or night shifts. 
3. A final phase allocates those working on particular day to the early or late shift on that day. 


For each nurse i and
each shift pattern j all the information concerning the desirability of the pattern for this nurse is captured in a
single numeric preference cost pij.

pij: Basic shift-pattern cost, general day / night preferences, specific requests, continuity
problems, number of successive working day, rotating nights / weekends and other working history information