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Re: find closest element of array without going over

by jds17 (Pilgrim)
on Jun 26, 2008 at 18:40 UTC ( #694252=note: print w/ replies, xml ) Need Help??

in reply to find closest element of array without going over

Hi, I am afraid I am reinventing the wheel here, but I had fun writing it, so here it goes. Comments:
1. It's just a binary search, as suggested by everyone else!
2. The performance should be quite good, but I did not test it against big arrays (and I would obviously need to write something to test against...)
3. In case two numbers in the array are equally close, the bigger number will be chosen as the winner.
Update: Of course I have to assume the target array is sorted.

use strict; use warnings; my @array = (1,4,5,6,7,9,10,23,34,44,55,56,57,59,70,80,90,100); print "\nenter number\n"; chomp (my $find = <STDIN>); my $nearest = @{nearest(\@array)}[0]; print "nearest to $find in array is: $nearest\n"; sub nearest { my ($a) = @_; my $size = @$a; return $a if $size == 1; my $mid = int(($size-1) / 2); my $test = @$a[$mid]; return $test <= $find ? (abs($test-$find)<abs(@$a[$mid+1]-$find) ? [$test] : $find <= @$a[$mid+1] ? [@$a[$mid+1]] : nearest([@$a[$mid+1 .. $ +size-1]])) : (abs($test-$find)<abs(@$a[$mid-1]-$find) ? [$test] : $find >= @$a[$mid-1] ? [@$a[$mid-1]] : nearest([@$a[0 .. $mid]] +)); }

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