Husband Wife Crossing Problem

husband_wife_crossing_solution.md

solved by: @sprimerano

mv | cross | left | right | return | left | right --- | --- | --- | --- |--- | --- | --- | ---

| -> xy | {A,B,Cz} | {x,y} | <- x | {Ax,B,Cz} | {x}

| -> xz | {A,B,C} | {x,y,z} | <- x | {Ax,B,C} | {y,z}

| -> BC | {Ax} | {By,Cz} | <- By | {Ax,By} | {Cz}

| -> AB | {x,y} | {A,B,Cz} | <- z | {x,y,z} | {A,B,C}

| -> xy | {z} | {Ax,By,C} | <- x | {x,z} | {A,By,C}

| -> xz | {} | {Ax,By,Cz}

problem.md

Three married couples, Al and Xenia, Bill and Yvette, and Carl and Zoe, are out for a hike when they come to a river. The good news is they find a boat; the bad news is the boat holds, at most, two people at a time. The problem is that the men are very amorous and will kiss any wife who is separated from her husband. The husbands are also very jealous, so how can the three couples cross the river without any illicit kissing occurring? Present your answer as a sequential list of the occupants of the boat as it makes multiple crossings of the river. To make grading easier, when there is an option for whom to put in the boat, choose the one or two eligible persons whose names come first alphabetically.

—The Chicken from Minsk by Yuri Chernyak and Robert Rose