I was trying to get my head around the binary search algorithm. I did it by comparing it to the linear search algorithm 

#!/usr/bin/perl
use warnings;
use v5.14;

# Find this word ...
my $find = shift // "";

# ... in this sorted list of words ...
my @words =
  qw(alpha bravo charlie delta echo foxtrot golf hotel india juliett k
+ilo lima mike november oscar papa quebec romeo sierra tango uniform v
+ictor whiskey xray yankee zulu);

# ... using two search algorithms
my %search = (
    linear => \&linsearch,
    binary => \&binsearch,
);

for my $alg ( sort keys %search ) {
    say "$alg searching '$find' in [@words] ...";

    my $idx = $search{$alg}->( $find, \@words );
    say defined $idx ? "found at index $idx" : "not found";
    say "";
}

sub binsearch {
    my ( $find, $array ) = @_;

    my $low  = 0;
    my $high = @$array - 1;

    while ( $low <= $high ) {
        my $try = int( ( $low + $high ) / 2 );
        say "--> trying at index $try";
        $low = $try + 1, next if $array->[$try] lt $find;
        $high = $try - 1, next if $array->[$try] gt $find;
        return $try;
    }
    return;
}

sub linsearch {
    my ( $find, $array ) = @_;

    for ( my $i = 0 ; $i < @$array ; $i++ ) {
        my $try = $i;
        say "--> trying at index $try";
        if ( $array->[$try] eq $find ) {
            return $try;
        }
    }
    return;
}

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In reply to Binary vs. linear search by reisinge

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