I have done a few different three day routines. The first routine is ok but exhausting due to training so many major muscle groups over the first three days. Second routine is fine except training back directly after shoulders tires out the rear delts. Personally i prefer the third routine. Even though training anything after legs is tiring shoulders are ok considering the only compound movment involved is pressing.
Day one Day one Day one
Chest and back Chest,tris,and calves Chest,tris,and calves
Day two Day two Day two
Shoulders,bis,and tris Back and shoulders Back,bis,and abs
Day three Day three Day thee
Legs ,abs ,and calves Legs,bis,and abs Legs and shoulders