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October 20th, 2011, 10:35 AM   #11
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Re: reverse n

Quote:
Originally Posted by vdrn
generalized expression of what comes after f(n)=
Isn't that what I just wrote? If not, explain what you mean by "generalized" and "expression".
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October 20th, 2011, 10:40 AM   #12
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Re: reverse n

Is there a formula for reversing n?
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October 20th, 2011, 01:07 PM   #13
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Re: reverse n

If you want a formula, a test for a palindrome is something like this:

Let m+1 be the amount of digits of your number
is the floorfunction
returns the absolute value of x
Evaluate
If it is 0, the number is palindrome, else not.
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October 20th, 2011, 02:22 PM   #14
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Re: reverse n

Quote:
Originally Posted by Hoempa
If you want a formula, a test for a palindrome is something like this:

Let m+1 be the amount of digits of your number
is the floorfunction
returns the absolute value of x
Evaluate
If it is 0, the number is palindrome, else not.
There are many ways test it. I was just putting things into some context with mentioning palindromic numbers. The real issue for me is how to reverse n.
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October 20th, 2011, 02:42 PM   #15
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Re: reverse n

Quote:
Originally Posted by vdrn
I was looking for a way to test if some, non-negative, integer n is a palindrome.
O, I'm sorry. I thought you where looking for a way to test if some, non-negative, integer n is a palindrome. And reversing the digits was to be a method to do so.
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October 20th, 2011, 03:22 PM   #16
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Re: reverse n

Quote:
Originally Posted by Hoempa
Quote:
Originally Posted by vdrn
I was looking for a way to test if some, non-negative, integer n is a palindrome.
O, I'm sorry. I thought you where looking for a way to test if some, non-negative, integer n is a palindrome. And reversing the digits was to be a method to do so.
"I was looking"...until I got interested in how would a formula for reversing n (part of testing n method) with the described properties look like.
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October 20th, 2011, 05:08 PM   #17
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Re: reverse n

What, then, do you mean by "formula"? Not function, because I gave a function and it wasn't what you wanted. Not polynomial -- there is no such polynomial.
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October 20th, 2011, 05:22 PM   #18
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Re: reverse n

How would you calculate the reverse of n then?
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October 21st, 2011, 01:10 AM   #19
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Re: reverse n

To reverse a positive integer, you need to know what its base 10 representation is, and to do so you need to work out each digit of the integer in base 10. We can write down a formula for each digit: where is the coefficient of in the decimal expansion of There is always a largest non-zero which we will denote The reverse of is given by There is no 'neater' way of doing this.
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October 21st, 2011, 05:59 AM   #20
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Re: reverse n

Quote:
Originally Posted by mattpi
To reverse a positive integer, you need to know what its base 10 representation is, and to do so you need to work out each digit of the integer in base 10. We can write down a formula for each digit: where is the coefficient of in the decimal expansion of There is always a largest non-zero which we will denote The reverse of is given by There is no 'neater' way of doing this.
Thanks! Do you know the source of this formula?
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