1. Write a logic for this program such that the transition can be done in the minimum number of moves possible.
2. As an extended exercise, write a program to solve the 15-puzzle completely.
With the right, systematic approach, these would be a matter of minutes, too.
When you learn how to bring a very systematic thinking to any problem-solving, solving even the most complex of problems becomes easy, simple, effortless and enjoyable.
Happy Programming 
Artistic Programming and Architecture & Design Consulting are offered to individuals as well as companies.
To know more about these offerings and to learn how to boost the efficiency and performance of individuals and project teams many-many times, write to artisticprogramming@reinventsoft.com