(;GM[1]FF[4]SZ[19]
GN[Undo]
PC[http://senseis.xmp.net/?YetAnotherNoviceTriesToWriteAGoProgram/MoveUndoDataStructureAndAlgorithm]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?YetAnotherNoviceTriesToWriteAGoProgram/MoveUndoDataStructureAndAlgorithm

Undo]
PL[W]

AB[aa][ba][ca][cb][db][ac][bc]
AW[da][ea][ab][eb][cc][dc][ad][bd][cd][ed]


;
)
