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 Day-knights and night-knights 8 (Posted on 2014-03-03)
There is a land where every inhabitant is either a day-knight or a night-knight. Day-knights tell the truth in the day and lie at night. Night-knights lie in the day and tell the truth at night.

Members of the Smith family are day-knights and, members of the Jones family are night-knights.

Four inhabitants Art, Barry, Cole and Dan approach a visitor to the island. It is known that precisely two of them are members of the Jones family and the remaining two are members of the Smith family.

They say:

Art: Barry’s last name is Smith.
Barry: Cole belongs to the Jones family.
Cole: Art and Dan are from different families.
Dan: Art and Barry are from the same family.

What are the surnames of the three inhabitants? Is it day or night?

 No Solution Yet Submitted by K Sengupta No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
 computer solution | Comment 3 of 4 |

DECLARE SUB permute (a\$)
CLS
a\$ = "ssjj": h\$ = a\$   '  for Art Barry Cole and Dan respectively
' s=smith-day; j=jones-night
DO
FOR day = 0 TO 1
truth\$ = MID\$("sj", 2 - day, 1)
good = 1
IF (MID\$(a\$, 1, 1) = truth\$) <> (MID\$(a\$, 2, 1) = "s") THEN good = 0
IF (MID\$(a\$, 2, 1) = truth\$) <> (MID\$(a\$, 3, 1) = "j") THEN good = 0
IF (MID\$(a\$, 3, 1) = truth\$) <> (MID\$(a\$, 1, 1) <> MID\$(a\$, 4, 1)) THEN good = 0
IF (MID\$(a\$, 4, 1) = truth\$) <> (MID\$(a\$, 1, 1) = MID\$(a\$, 2, 1)) THEN good = 0
IF good THEN PRINT MID\$("dn", 2 - day, 1); "  "; a\$
NEXT

permute a\$
LOOP UNTIL a\$ = h\$

finds

d  jjss

meaning it is daytime and Art and Barry are Joneses and Cole and Dan are Smiths.

 Posted by Charlie on 2014-03-03 13:17:00

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