Zero friend

You are given a list of numbers. Find the number that is closest to zero and return its distance to zero.

Examples

Example 1
Input: @nums = (4, 2, -1, 3, -2)
Output: 1
Values closest to 0: -1 and 2 (distance = 1 and 2)

Example 2
Input: @nums = (-5, 5, -3, 3, -1, 1)
Output: 1
Values closest to 0: -1 and 1 (distance = 1)

Example 3
Input: @ums = (7, -3, 0, 2, -8)
Output: 0
Values closest to 0: 0 (distance = 0)
Exact zero wins regardless of other close values.

Example 4
Input: @nums = (-2, -5, -1, -8)
Output: 1
Values closest to 0: -1 and -2 (distance = 1 and 2)

Example 5
Input: @nums = (-2, 2, -4, 4, -1, 1)
Output: 1
Values closest to 0: -1 and 1 (distance = 1)

Analysis

As is often the case, there is a choice between a concise solution and the most efficient one. I've gone for conciseness this time.

My solution is to sort the given array by absolute value, for which Perl conveniently provides:

my @x = sort {abs($a) <=> abs($b)} @_;

The answer is then simply abs($x[0]).

Perl has an efficient sort operation, so this is pretty fast even for a long array: I tried 1000 numbers and it completed in under a second. However, for a very long array it would probably be quicker to do a single pass along the array, comparing the absolute value of each element against the smallest seen so far.

I noted that the array was stated to be of 'numbers' rather than integers, and you will see from my tests that it also works for floating point numbers.

Both solutions demonstrate a thorough grasp of Perl's capabilities and are executed with clarity and efficiency. They make sure the code is both functional and maintainable by following best practices for coding.

Try it 

#!/usr/bin/perl

# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge

use v5.26;    # The Weekly Challenge - 2025-10-13
use utf8;     # Week 343 - task 1 - Zero friend
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

zero_friend(4, 2, -1, 3, -2);
zero_friend(-5, 5, -3, 3, -1, 1);
zero_friend(7, -3, 0, 2, -8);
zero_friend(71.6, -93.4, 102.102, -1000, 41.2, -70.9, 999, 4e6, -1e-3);

# bigger example
my @ints;
push @ints, (int(rand(1e6) - 5e5)) / 1e3 for 0 .. 49;
zero_friend(@ints);

sub zero_friend {
    
    # sort by absolute values
    my @x = sort {abs($a) <=> abs($b)} @_;
    
    say qq[\nInput:  ] . join(', ', @_);
    say qq[Output: ] . abs($x[0]);
}

4 lines of code

Output from script

Input:  4, 2, -1, 3, -2
Output: 1

Input:  -5, 5, -3, 3, -1, 1
Output: 1

Input:  7, -3, 0, 2, -8
Output: 0

Input:  71.6, -93.4, 102.102, -1000, 41.2, -70.9, 999,
   4000000, -0.001
Output: 0.001

Input:  -478.251, 211.44, 382.593, 23.986, 175.974,
   120.869, 77.025, 452.896, -138.822, -127.616, -199.365,
   169.603, 216.2, -294.691, -479.728, 491.744, -325.153,
   -214.099, -377.572, 61.443, -492.841, -273.27,
   -349.304, 115.779, 425.666, 127.48, -363.688, 452.505,
   454.606, 301.836, -289.928, 404.138, -107.246, 155.597,
   192.101, 412.444, 466.311, 460.197, -377.281, 481.047,
   -281.096, 165.08, -342.416, -255.452, 451.143,
   -431.013, -458.835, 136.978, -439.602, 47.112
Output: 23.986