How to get biggest char from string
How do I get the char with the biggest ascii value from a string?
$str = 'abcb'
# extract biggest char somehow
# as a resu开发者_如何学JAVAlt $char contains "c"
use List::Util 'maxstr';
my $maxChar = maxstr split //, 'abcb'; # 'c'
The trick with these things is to know your other constraints. How often will you need to do this in your program and how big is the string? With a single shot short string, you can get away with waste. If you have to do it repeatedly or for large strings, that waste matters much more.
I test it for 5 CPU seconds on (Mac Pro, OS X.6.8, Perl 5.14.1) for increasing orders of magnitude in string length:
+-------------------------------------------------+
| Iterations |
+-----------------+---------+---------+---------+---------+---------+
| Sub name | 10**1 | 10**2 | 10**3 | 10**4 | 10**5 |
+-----------------+---------+---------+---------+---------+---------+
| iterate_foreach | 983840 | 141997 | 16333 | 1686 | 168 |
| iterate_for | 1041713 | 146608 | 15370 | 1538 | 155 |
| sorter | 1194656 | 120608 | 10490 | 888 | 82 |
| maxstr | 1505280 | 180923 | 19764 | 2120 | 202 |
| control | 8019246 | 8019246 | 7719377 | 5041132 | 710027 |
+-----------------+---------+---------+---------+---------+---------+
List::Util's maxstr
dominates in all cases. For the first order, a string of 10 characters, sorter
does okay. After that, sorter
gets worse and worse, as you should expect. The iterate_foreach
and iterate_for
degrade much better.
The code:
use 5.010;
use strict;
use warnings;
use Benchmark;
use List::Util;
my $count = -5;
foreach my $order ( 1 .. 5 ) {
say "-" x 50, "\nTiming for order $order";
my $string = make_string( $order );
timethese( $count, {
'sorter' => sub { my $c = sorter( $string ) },
'maxstr' => sub { my $c = maxstr( $string ) },
'iterate_for' => sub { my $c = iterate_for( $string ) },
'iterate_foreach' => sub { my $c = iterate_foreach( $string ) },
'control' => sub { my $c = control( $string ) },
});
}
sub make_string {
my $order = shift;
my $string;
for( my $i = 0; $i < 10**$order; $i++ ) {
$string .= chr int rand 256;
}
$string;
}
sub sorter {
my $str = shift;
my $char = (sort split //, $str)[-1];
}
sub maxstr {
my $str = shift;
my $char = List::Util::maxstr( split //, $str );
}
sub iterate_for {
my $str = shift;
my $length = length $str;
my $max = '';
for( my $i = 0; $i < $length; $i++ ){
my $chr = substr( $str, $i, 1 );
$max = $chr if $chr gt $max;
}
return $max;
}
sub iterate_foreach {
my $str = shift;
my $max = '';
foreach ( split //, $str ){
$max = $_ if $_ gt $max;
}
return $max;
}
sub control {
my $str = shift;
return 'a';
}
$str = 'abcb';
@a = sort split(//, $str);
$char = pop(@a);
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