You're once again on the island of Knights, Knaves, and Liars. You meet 6 natives who are all different ages between 20 and 50. They make the following statements to you:

Andy says:

Brad is a Liar.
Fred is a Liar.
I'm one year older than Brad.
I'm three years older than Chet.
The sum of our ages is divisible by 3.

Brad says:

Chet is a Liar.
Andy is a Liar.
I'm one year older than Chet.
I'm three years older than Doug.
My age is divisible by 5.

Chet says:

Doug is a Liar.
Brad is a Liar.
I'm one year older than Doug.
I'm three years older than Eddy.
My age is divisible by 2.

Doug says:

Eddy is a Liar.
Chet is a Liar.
I'm one year older than Eddy.
I'm three years older than Fred.
I'm the oldest.

Eddy says:

Fred is a Liar.
Doug is a Liar.
I'm one year older than Fred.
I'm three years older than Andy.
The sum of our ages is divisible by 11.

Fred says:

Andy is a Liar.
Eddy is a Liar.
I'm one year older than Andy.
I'm three years older than Brad.
The sum of our ages is a perfect square.

Figure out the ages of the six natives.

DECLARE SUB permute (a$)
DIM used(20 TO 50)
OPEN "liar logic 2.txt" FOR OUTPUT AS #2
CLS
FOR At = 0 TO 3 'Liar, Kv-2nd true, Kv-1st true, Kt
 a1 = -(At \ 2): a2 = -(At MOD 2)
 FOR Bt = 0 TO 3
  b1 = -(Bt \ 2): b2 = -(Bt MOD 2)
  FOR Ct = 0 TO 3
   c1 = -(Ct \ 2): c2 = -(Ct MOD 2)
   FOR Dt = 0 TO 3
    d1 = -(Dt \ 2): d2 = -(Dt MOD 2)
    FOR Et = 0 TO 3
     e1 = -(Et \ 2): e2 = -(Et MOD 2)
     FOR Ft = 0 TO 3
      f1 = -(Ft \ 2): f2 = -(Ft MOD 2)

      good = 1
      IF a1 <> (Bt = 0) THEN good = 0
      IF a2 <> (Ft = 0) THEN good = 0
      IF b1 <> (Ct = 0) THEN good = 0
      IF b2 <> (At = 0) THEN good = 0
      IF c1 <> (Dt = 0) THEN good = 0
      IF c2 <> (Bt = 0) THEN good = 0
      IF d1 <> (Et = 0) THEN good = 0
      IF d2 <> (Ct = 0) THEN good = 0
      IF e1 <> (Ft = 0) THEN good = 0
      IF e2 <> (Dt = 0) THEN good = 0
      IF f1 <> (At = 0) THEN good = 0
      IF f2 <> (Et = 0) THEN good = 0
      IF good THEN
       PRINT
       PRINT At; Bt; Ct; Dt; Et; Ft; "*"
       PRINT #2, At; Bt; Ct; Dt; Et; Ft; "*"
       FOR aage = 20 TO 50
        used(aage) = 1
        PRINT aage;
        FOR bage = 20 TO 50
         IF used(bage) = 0 THEN
          used(bage) = 1
          FOR cage = 20 TO 50
           IF used(cage) = 0 THEN
            used(cage) = 1
            FOR dage = 20 TO 50
             IF used(dage) = 0 THEN
              used(dage) = 1
              FOR eage = 20 TO 50
               IF used(eage) = 0 THEN
                used(eage) = 1
                FOR fage = 20 TO 50
                 IF used(fage) = 0 THEN
                  used(fage) = 1

                  sum = aage + bage + cage + dage + eage + fage
                  good = 1
                  IF a1 <> (aage = bage + 1) THEN good = 0
                  IF a2 <> (aage = cage + 3) THEN good = 0
                  IF a1 <> (sum MOD 3 = 0) THEN good = 0
                  IF good THEN
                   IF b1 <> (bage = cage + 1) THEN good = 0
                   IF b2 <> (bage = dage + 3) THEN good = 0
                   IF b1 <> (bage MOD 5 = 0) THEN good = 0
                   IF good THEN
                    IF c1 <> (cage = dage + 1) THEN good = 0
                    IF c2 <> (cage = eage + 3) THEN good = 0
                    IF c1 <> (cage MOD 2 = 0) THEN good = 0
                    IF good THEN
                     IF d1 <> (dage = eage + 1) THEN good = 0
                     IF d2 <> (dage = fage + 3) THEN good = 0
                     IF d1 <> (dage > aage AND dage > bage AND dage > cage AND dage > eage AND dage > fage) THEN good = 0
                     IF good THEN
                      IF e1 <> (eage = fage + 1) THEN good = 0
                      IF e2 <> (eage = aage + 3) THEN good = 0
                      IF e1 <> (sum MOD 11 = 0) THEN good = 0
                      IF good THEN
                       IF f1 <> (fage = aage + 1) THEN good = 0
                       IF f2 <> (fage = bage + 3) THEN good = 0
                       sr = INT(SQR(sum) + .5)
                       IF f1 <> (sr * sr = sum) THEN good = 0
                       IF good THEN
                        PRINT
                        PRINT At; Bt; Ct; Dt; Et; Ft
                        PRINT aage; bage; cage; dage; eage; fage, sum, SQR(sum)
                        PRINT #2, aage; bage; cage; dage; eage; fage, sum, SQR(sum)
                       END IF
                      END IF
                     END IF
                    END IF
                   END IF
                  END IF
                  used(fage) = 0

                 END IF

                NEXT fage
                used(eage) = 0
               END IF
              NEXT eage
              used(dage) = 0
             END IF
            NEXT dage
            used(cage) = 0
           END IF
          NEXT cage
          used(bage) = 0
         END IF
        NEXT bage
        used(aage) = 0

       NEXT aage

      END IF

     NEXT
    NEXT
   NEXT
  NEXT
 NEXT
NEXT

 

produces the following:

 0  1  2  0  1  2 *
 0  3  0  3  0  3 *
 1  2  0  1  2  0 *
 42  40  39  31  29  28   209     14.45683
 2  0  1  2  0  1 *
 3  0  3  0  3  0 *

Each line with an asterisk shows a set of native types, from Andy to Fred in order, that are consistent with their first two claims each. Zero represents a liar; 1 represents a knave who starts with a lie; 2, a knave who starts with a true statement; and 3, a knight.

Only one of these is followed by a set of ages consistent with their statements and types:

Andy is a 42-year-old knave, who started with a lie.
Brad is a 40-year-old knave, who started with a true statement.
Chet is a 39-year-old liar.
Doug is a 31-year-old knave, who started with a lie.
Eddy is a 29-year-old knave, who started with a true statement.
Fred is a 28-year-old liar.

209 is the sum of their ages, which is not a perfect square, but is divisible by 11.

Posted by Charlie on 2014-03-17 16:25:04