Re^3: Challenge: Nearest Palindromic Number


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Re^3: Challenge: Nearest Palindromic Number

by Limbic~Region (Chancellor)

on Feb 03, 2005 at 13:13 UTC ( [id://427613]=note: print w/replies, xml )

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in reply to Re^2: Challenge: Nearest Palindromic Number
in thread Challenge: Nearest Palindromic Number

tilly,
For the record, Roy Johnson was the first to produce working code. Unfortunately it was broken during some refactoring. The code that I validated originally was:

sub nearest {
    my $num = shift;
    my $firstlen = int(length($num)/2 + .5);
    my $first = substr($num, 0, $firstlen);
    my $back = reverse($first);
    substr($back, 0, 1, '') if $firstlen > length($num)/2;
    # Update (again): if higher, check lower and vice-versa:
    my $one = $first . $back;

    $first += $one < $num ? 1 : -1;
    $back = reverse($first);
    substr($back, 0, 1, '') if $firstlen > length($num)/2;
    my $two = $first . $back;

    return abs( $one - $num ) < abs( $two - $num)  ? $one : $two;
}
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Cheers - L~R