Google Programming Brainteaser

[Fred Bloggs]

The problem is to compute the resistance between terminals A-B,
separated by a "knight's move", in an infinite two dimensional grid of
equal value resistors- closed form solution in this case:

View in a fixed-width font such as
Courier.


.
.
.
. | | | |
. -+---[R]---+---[R]---+---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | | | |
. -+---[R]---+---[R]---+---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | | |* |
. -+---[R]---+---[R]---B---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | | | |
. -+---[R]---+---[R]---+---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | |* | |
. -+---[R]---A---[R]---+---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | | | |
. -+---[R]---+---[R]---+---[R]---+-
. | | | |
. [R] [R] [R] [R]
. | | | |
.