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#!/usr/bin/env perl
# vim:set ts=4 sw=4 sts=4 et ai wm=0 nu:
#=============================================================================
# Copyright (c) 2025, Bob Lied
#=============================================================================
# ch-2.pl Perl Weekly Challenge 345 Task 2 Last Visitor
#=============================================================================
# You are given an integer array @ints where each element is either a
# positive integer or -1. We process the array from left to right while
# maintaining two lists:
# @seen: stores previously seen positive integers (newest at the front)
# @ans: stores the answers for each -1
#
# Rules:
# If $ints[i] is a positive number -> insert it at the front of @seen
# If $ints[i] is -1:
# Let $x be how many -1s in a row we’ve seen before this one.
# If $x < len(@seen) -> append seen[x] to @ans
# Else -> append -1 to @ans
#
# At the end, return @ans.
#
# Example 1 Input: @ints = (5, -1, -1)
# Output: (5, -1)
# @seen = (5)
# First -1: @ans = (5)
# Second -1: @ans = (5, -1)
# Example 2 Input: @ints = (3, 7, -1, -1, -1)
# Output: (7, 3, -1)
# @seen = (3, 7)
# First -1: @ans = (7)
# Second -1: @ans = (7, 3)
# Third -1: @ans = (7, 3, -1)
# Example 3 Input: @ints = (2, -1, 4, -1, -1)
# Output: (2, 4, 2)
# Example 4 Input: @ints = (10, 20, -1, 30, -1, -1)
# Output: (20, 30, 20)
# Example 5 Input: @ints = (-1, -1, 5, -1)
# Output: (-1, -1, 5)
#=============================================================================
use v5.42;
use Getopt::Long;
my $Verbose = false;
my $DoTest = false;
my $Benchmark = 0;
GetOptions("test" => \$DoTest, "verbose" => \$Verbose, "benchmark:i" => \$Benchmark);
my $logger;
{
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init({ level => ($Verbose ? $DEBUG : $INFO ),
layout => "%d{HH:mm:ss.SSS} %p{1} %m%n" });
$logger = Log::Log4perl->get_logger();
}
#=============================================================================
exit(!runTest()) if $DoTest;
exit( runBenchmark($Benchmark) ) if $Benchmark;
say '(', join(", ", lastVisitor(@ARGV)->@*), ')';
#=============================================================================
sub lastVisitor(@int)
{
my @seen = ();
my @ans = ();
my $x = 0; # Count of consecutive -1s
for ( @int )
{
if ( $_ > 0 )
{
$x = 0;
unshift @seen, $_;
}
else
{
if ( $x < @seen )
{
push @ans, $seen[$x];
}
else
{
push @ans, -1;
}
$x++;
}
}
return \@ans;
}
sub runTest
{
use Test2::V0;
is( lastVisitor( 5, -1, -1 ), [ 5, -1 ], "Example 1");
is( lastVisitor( 3, 7, -1, -1, -1 ), [ 7, 3, -1], "Example 2");
is( lastVisitor( 2, -1, 4, -1, -1 ), [ 2, 4, 2], "Example 3");
is( lastVisitor(10, 20, -1, 30, -1, -1), [20, 30, 20], "Example 4");
is( lastVisitor(-1, -1, 5, -1 ), [-1, -1, 5], "Example 5");
done_testing;
}
sub runBenchmark($repeat)
{
use Benchmark qw/cmpthese/;
cmpthese($repeat, {
label => sub { },
});
}
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