Bishop Problem

chess

#1

If bishop is currently on the cell (r,c) of an empty chessboard. What will be the algorithm to move the bishop to the cell (r1,c1) using as few moves as possible.
example:
Question:
The bishop can go from (4,6) to (7,3) in a single move.
Answer:
No. of moves will be: 1


#2

another similar chess problem: www.spoj.com/problems/NAKANJ