Draw a line following the grid lines conforming the the following rules:
1  The line starts from S and ends at F.
2  The line does not cross or overlap itself at any point.
3  The line divides the grid into regions each with exactly two As and two Bs.
+++++F
 A  B  A   B 
++++++
  B    B 
++++++
 A   B   A 
++++++
 A  A   A  B 
++++++
 B   B   A 
S+++++
An example of a solved grid:
+ + +F
B A  A
+++ +
 B
S + + +
(In reply to
re: Strange by Charlie)
I also gave up, but your post give me the desire to take a look, and the first solution I proved, that was it.
+++++F
 A  B  A   B 
+===+===+===+===+===^
  B    B 
^+v===+===+===+
 A   B   A 
^v===++===+===^
 A  A   A  B 
^===++===^++
 B   B   A 
S=======^+++

Posted by armando
on 20160429 11:20:54 