Five programming problems every Software Engineer should be able to solve in less than 1 hour

[Mark Waddingham]

> I thought briefly about doing this but it didn't gel in my mind as 
> quickly
> as the substitution method I used. I quite like how this turned out!

I realized after posting my versions that my version of problem5 could 
be even more succinct code-wise:

function problem5
    local tResults
    repeat with i = 0 to 3^8
       local tScheme, tSum
       put empty into tSum
       put format("%08s", baseConvert(i, 10, 3)) & "0" into tScheme
       repeat with j = 1 to 9
          put j after tSum
          put item (char j of tScheme + 1) of ",+,-" after tSum
       end repeat
       if value(tSum) is 100 then
          put tSum & return after tResults
       end if
    end repeat
    return tResults
end problem5

Although it is perhaps a little more opaque.

It's an interesting problem - the 'enumerate all permutations and then 
evaluate' approach (which I think is essential what both your's and mine 
are) certainly works in this smaller case as there are only 3^8 
permutations.

Generally though I suspect some element of dynamic programming (i.e. 
caching the value of subsequences) and recursion would be more tractable 
if the number of digits was greater.

-- 
Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps