Ken's answer to Howie's filePro Quiz # 1
Here is Ken's answer to my first little filePro quiz: The question was: What is the filename that the below routine always generates?
If:
1 Then: gosub passwd
If:
2 Then: end
If: '*** Try to figure out the name of the password processing table
3 Then: '*** called by line number 16 - ***without using the debugger***
passwd If:
4 Then: s(5,.0) = mid(@tm,"1","2") * mid(@tm,"4","2") * mid(@tm,"7","2")
If:
5 Then: s = s + mid(@tm,"7","2")
If:
6 Then: an(5,.0) = rand(s)
If:
7 Then: va(5,.0) = (mod(an,"9") + "1")
If:
8 Then: va = "9" * va
If:
9 Then: f(5) = mid(va,"5","1") - mid(va,"1","1") + mid(va,"4","1")
If:
10 Then: f = f - mid(f,"4",mid(f,"4","1"))
If:
11 Then: f = f - mid(va,"3","1") + mid(va,"2","1")
If:
12 Then: fn(3) = "" { f - "1" { f - "2" {f - "3"
If:
13 Then: fn = fn + "123"
If:
14 Then: fn = fn / ("1" { mid(fn,"3","1"))
If:
15 Then: fn = ( "" { fn { chr(fn) ) - "11"
If:
16 Then: call (fn) '=======What's the filename?
If:
17 Then: return
And here is Ken's explaination:
answer is "524"
It only took a couple of minutes in my head.
[...]
If:
6 Then: n(5,.0) = rand(s)
Using random numbers, when you know the answer is fixed. Hint that this
number is irrelevent.
If:
7 Then: a(5,.0) = (mod(an,"9") + "1")
make a random number 1 to 9.
If:
8 Then: va = "9" * va
"a" is now a multiple of 9 from 9 to 81.
If:
9 Then: f(5) = mid(va,"5","1") - mid(va,"1","1") + mid(va,"4","1")
multiples of 9 always have the sum of their digits add up to 9, and since
the max value of 'va' at this point is 81, f must be "9".
If:
10 Then: f = f - mid(f,"4",mid(f,"4","1"))
is still "9" as the mid is always blank.
If:
11 Then: f = f - mid(va,"3","1") + mid(va,"2","1")
still "9" as the mid's are always blank.
If:
12 Then: fn(3) = "" { f - "1" { f - "2" {f - "3"
fn is "876"
If:
13 Then: fn = fn + "123"
fn is "999"
If:
14 Then: fn = fn / ("1" { mid(fn,"3","1"))
(fn/"19")
fn is "53". (Okay, I used a calculator here.)
If:
15 Then: fn = ( "" { fn { chr(fn) ) - "11"
"53" { "5" = "535" "535" - "11" = "524"
fn is "524"
Couldn't have explained it better myself. Thanks Ken. Hope you enjoyed my quiz. Stop back to see new ones as they are posted.
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