Subj : Re: puzzle
To   : comp.programming
From : Joe Seigh
Date : Sun Jul 10 2005 02:02 pm

CBFalconer wrote:
> spinoza1111@yahoo.com wrote:
> 
> ... snip ...
> 
>>in this thread, I have repeatedly acknowledged that I did not have
>>enough erudition to think of, or in my case from grad school
>>remember, the XOR solution.
> 
> ... snip further pointless erudition ...
> 
> FYI, the entire secret of the XOR solution is exposed in the
> following truth table:
> 
>    a     b      XOR(a,b)
>    =     =      ========
>    F     F        F
>    F     T        T
>    T     F        T
>    T     T        F
> 
> Some have been known to learn this without attending grad school.
> 

To make things interesting, this problem should be reposed as,
you have a unordered sequence of the numbers 0 to n with one
number missing and the others appearing only once.  Find two
O(n) ways of determining the missing number.

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

.