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How can I find the index of the biggest element in an array?

by Anonymous Monk
on Mar 08, 2001 at 08:03 UTC ( #62913=categorized question: print w/replies, xml ) Need Help??
Contributed by Anonymous Monk on Mar 08, 2001 at 08:03 UTC
Q&A  > arrays


Answer: How can I find the index of the biggest element in an array?
contributed by GrandFather

Given an array @data containing numeric data:

my $idxMax = 0; $data[$idxMax] > $data[$_] or $idxMax = $_ for 1 .. $#data;

is not only compact but, somewhat surprisingly perhaps, comparable in speed to caching $data[$idxMax] as shown in most of the other variants. A cache variant is worth using if an expensive calculation is required in the comparison or a very large array is being processed.

Answer: How can I find the index of the biggest element in an array?
contributed by tye

my $index = 0; my $maxval = $myarray[ $index ]; for my $i ( 0 .. $#myarray ) { $maxval < $myarray[$i] and $index = $i if $maxval < $myarray[$i]; } print "The greatest is element number $index: $myarray[$index]\n";
Answer: How can I find the index of the biggest element in an array?
contributed by satchboost

my $index = 0; my $maxval = $myarray[ my $index ]; for ( 0 .. $#myarray ) { if ( $maxval < $myarray[$_] ) { $index = $_; $maxval = $myarray[$_]; } } print "Max is index $index: $myarray[$index]\n";
Answer: How can I find the index of the biggest element in an array?
contributed by turnstep

my $max; my $index; my $x = 0; for ( @myarray ) { $index = $x and $max = $_ if !defined $max or $_ > $max; $x++; } print "The winner is element number $index: $myarray[$index]\n";
Answer: How can I find the index of the biggest element in an array?
contributed by reisinge

A one-liner where the array elements are the command line arguments:

$ perl -E 'say [ sort { $ARGV[$b] <=> $ARGV[$a] } 0..$#ARGV ]->[0]' 42 + 1000 999 0 -1
Answer: How can I find the index of the biggest element in an array?
contributed by DillonYu

Use mod:://List::Util's reduce:

use List::Util qw /reduce/; my @arr= qw/7 6 4 90 5 7/; my $index = reduce {$arr[$a] > $arr[$b] ? $a : $b} (0 .. $#arr); print "$index\n";
Answer: How can I find the index of the biggest element in an array?
contributed by salva

and if what you need are the indexes for the $n biggest elements:

use Sort::Key::Top qw(nkeytop rnkeytop); my @data = ( 100, -2, 5, 12, 1, 1, 6786, ...); my @min_ix_n = nkeytop { @data[$_] } $n => 0..$#data; my @max_ix_n = rnkeytop { @data[$_] } $n => 0..$#data;
Answer: How can I find the index of the biggest element in an array?
contributed by jdporter

A recursive solution.

sub _index_of_largest { my $X = shift; my $L = shift; my $x = $#_; my $l = pop; defined $X and $L > $l and ($x,$l) = ($X,$L); @_ or return $x; unshift @_, $x, $l; goto &_index_of_largest } sub index_of_largest { @_ or die; _index_of_largest(undef,undef,@_); } my $i = index_of_largest( @a );
Answer: How can I find the index of the biggest element in an array?
contributed by Skeeve

my $i = $#data; my $max = $i; $max = $data[$i] > $data[$max] ? $i : $max while $i--; print "Max value is $data[$max], at index $max\n"

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