challenge for programmable calculators

[Don Shepherd]

(12-21-2013 11:26 PM)Gerson W. Barbosa Wrote:  

(12-21-2013 10:26 PM)Katie Wasserman Wrote:  

Code:


%%HP: T(3)A(D)F(.);
\<< 1. 9.
FOR a 1. 9.
FOR b a SQ b * a b SQ * + 1. - NEG DUP SQ a b * 4. * a 100. * b 10. * + * + \v/ + a b * 2. * / DUP FP NOT NOT { DROP } { DUP 10. < { a 100. * b 10. * + + } { DROP } IFTE } IFTE
NEXT
NEXT
\>>

Nice use of the quadratic formula to save the inner-most loop -- compared to the brute force solution. I wonder if there's an even better way.

Perhaps one should analyze the formula and limit the outer loop (I haven't done that). BTW, I have to say "my" method is kind of cheating, since the hard work was done by W|A:

solve a*b*c*(a+b+c)==100*a+10*b+c for a, b and c

Gerson, I've never used Wolfram Alpha, but from your link, it does not appear to give the actual answer, ie, the two numbers.