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Klick

Thu May 18, 2006 5:57 pm


Number Conversion help

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As a part of my ecryption program for class, I would 5 numbers to be put into 1 large number, by the following sequence:

8,24,7,0,3

Large Number = 8 * (27**4) + 24 * (27**3) + 7 * (27**2) + 0 * (27**1) + 3 * (27 **0)

The number in this case would be 4729026. 
Converting the 5 numbers into 1 number was fairly simple to figure out on my own. I need help recovering numbers from that large number.

I figure that i can do this using mod by the series of powers of 27, and then subtract the remainder from the total

Like so:

var largenum : int
var smallnums : array 1 .. 5 of int
var power :int := 1

largenum := 8 * (27 ** 4) + 24 * (27 ** 3) + 7 * (27 ** 2) + 0 * (27 ** 1) + 3 * (27 ** 0)

for decreasing i : 5 .. 1
    smallnums (i) := largenum 
    smallnums (i) := smallnums (i) mod 27 ** power
    largenum -= smallnums (i)
    power += 1
end for

for i : 1 .. 5
    put smallnums (i), "," ..
end for


It works for the last 2 numbers for some, reason, but fails miserably on the first 3.

The problem I think, is the way I am approching the solution, or I am missing something important. Any suggestions or help will be greatly appreciated.

Much Thanks!


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TheOneTrueGod

Thu May 18, 2006 6:27 pm



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for decreasing i : 4 .. 0
    put largenum div 27 ** i
    largenum -= (largenum div 27 ** i) * 27 ** i
end for


Yarr, sorry for doing it entirely for you, its generally against my policy to do that, but I couldn't get this one after half a second of looking at it, so I tinkered with it till I got it :P

I will now attempt to explain where you went wrong.


for decreasing i : 5 .. 1 
    smallnums (i) := largenum 
    smallnums (i) := smallnums (i) mod 27 ** power 
    largenum -= smallnums (i) 
    power += 1 
end for 


The above is your code.  Lets pick an arbitrary letter to represent what the first number is.  I like n, so lets go with that.  If we divide the "largenum" by 27**4, the resulting number will be between n * 27**4 and (n+1)*27**4.  Therefore, if we truncate that number, we will get what n is.  Now, just subtract n * 27**4 from the large number and repeat.  One other error you made in yours is "power" started at 1, when it should have started at zero (look at the largenum calculation).


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Klick

Thu May 18, 2006 6:37 pm



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You really are TheOneTrueGod!! I knew i was missing something in it, just couldn't figure it out. Thanks a bunch. This will really help me out alot.

Thanks again!