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use v6d;
################################################################################
=begin comment
Perl Weekly Challenge 252
=========================
TASK #2
-------
*Unique Sum Zero*
Submitted by: Mohammad S Anwar
You are given an integer, $n.
Write a script to find an array containing $n unique integers such that they add
up to zero.
Example 1
Input: $n = 5
Output: (-7, -1, 1, 3, 4)
Two other possible solutions could be as below:
(-5, -1, 1, 2, 3) and (-3, -1, 2, -2, 4).
Example 2
Input: $n = 3
Output: (-1, 0, 1)
Example 3
Input: $n = 1
Output: (0)
=end comment
################################################################################
#--------------------------------------#
# Copyright © 2024 PerlMonk Athanasius #
#--------------------------------------#
#===============================================================================
=begin comment
Assumption
----------
It is assumed that the output list contains at least one element, and therefore
that $n > 0.
Interface
---------
1. A single, non-zero, positive integer should be entered on the command-line.
2. No test suite is provided, as the output is randomized. Instead, if the
constant DEBUG is set to True, the generated solution is validated to ensure
that it contains exactly $n unique elements that sum to zero.
3. The constant COEFF may be adjusted to vary the range of potential output
values. For example, if $n = 4 and COEFF = 2.5, the integers in the solution
will be drawn from the range -10 .. +10.
=end comment
#===============================================================================
use List::Util < shuffle >;
subset Pos of Int where * > 0;
my Rat constant COEFF = 2.5; # Determines range of possible solution values
my Bool constant DEBUG = True;
#-------------------------------------------------------------------------------
BEGIN
#-------------------------------------------------------------------------------
{
"\nChallenge 252, Task #2: Unique Sum Zero (Raku)\n".put;
}
#===============================================================================
sub MAIN
(
Pos:D $n #= A non-zero, positive integer
)
#===============================================================================
{
"Input: \$n = $n".put;
my Int @zero-sum-list = find-zero-sum-list( $n );
"Output: (%s)\n".printf: @zero-sum-list.join: ', ';
validate( $n, @zero-sum-list ) or die 'Solution failed validation' if DEBUG;
}
#-------------------------------------------------------------------------------
sub find-zero-sum-list( Pos:D $n --> List:D[Int:D] )
#-------------------------------------------------------------------------------
{
my Int @zero-sum-list;
my UInt $max = (COEFF * $n).floor;
loop (my Bool $done = False; !$done; )
{
my Int @candidates = -$max .. +$max;
@zero-sum-list = (shuffle @candidates)[ 0 .. $n - 2 ];
my Int $diff = - [+] @zero-sum-list;
# Ensure that $diff is (1) not already in @zero-sum
# and (2) within the specified range
if @zero-sum-list.none == $diff && $diff.abs <= $max
{
@zero-sum-list.push: $diff;
$done = True;
}
}
return @zero-sum-list;
}
#-------------------------------------------------------------------------------
sub validate( Pos:D $n, List:D[Int:D] $zero-sum-list --> Bool:D )
#-------------------------------------------------------------------------------
{
# 1. n elements
return False unless $zero-sum-list.elems == $n;
# 2. Unique
my Pos %dict{Int};
for @$zero-sum-list -> Int $elem
{
return False unless ++%dict{ $elem } == 1;
}
# 3. Add up to zero
my Int $sum = [+] @$zero-sum-list;
return $sum == 0;
}
#-------------------------------------------------------------------------------
sub USAGE()
#-------------------------------------------------------------------------------
{
my Str $usage = $*USAGE;
$usage ~~ s:g/ ($*PROGRAM-NAME) /raku $0/;
$usage.put;
}
################################################################################
|
