Discussion on: Daily Coding Puzzles - Nov 11th - Nov 16th

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Replies for: Thursday - Queue from two stacks (Hacker Rank Medium) Complete the put, pop, and peek methods in the editor below. They must perform the actions ...

Perl solution. Passes all the tests on HackerRank.

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package Queue;

    use enum qw( LIFO FIFO );

    sub new  { bless [[], []], shift }
    sub Push { push @{ $_[0][LIFO] }, $_[1]; }
    sub Pop  { @{ $_[0][FIFO] } or $_[0]->_restack; pop @{ $_[0][FIFO] }; }
    sub Peek { @{ $_[0][FIFO] } or $_[0]->_restack; say $_[0][FIFO][-1]; }
    sub _restack {
        push @{ $_[0][FIFO] }, pop @{ $_[0][LIFO] } while @{ $_[0][LIFO] };
    }
}

my %dispatch = (
    1 => 'Push',
    2 => 'Pop',
    3 => 'Peek',
);

my $q = 'Queue'->new;

<>;  # skip the 1st line.
while (<>) {
    my ($operation, $argument) = split;
    $q->${\$dispatch{$operation}}($argument);
}