Subj : Re: puzzle
To   : comp.programming
From : cri
Date : Mon Jul 11 2005 05:15 am

On Sun, 10 Jul 2005 21:35:01 GMT, cri@tiac.net (Richard Harter) wrote:


>Method 2:  Determine the sum of the numbers 0...n, then the sum of the
>sequence.  The difference of the two sums is the missing number.  To
>avoid overflow/underflow do the sums module n+1.

A prettier way to do this is to compute sum(i -a[i]) for i=1...n
Alternatively subtract sum(a[i]) from n*(n+1)/2.


Richard Harter, cri@tiac.net
http://home.tiac.net/~cri, http://www.varinoma.com
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