#!/usr/bin/env perl

use strict;
use warnings;

use constant {
    INPUT => 0,
    TARGET => 1,
    EXPECTED => 2,
};

use Test::More;

my @tests = (
    [[2,7,11,15], 9, [0, 1]],
    [[3,2,4], 6, [1,2]],
    [[3,3], 6, [0,1]],
);

plan tests => 0+@tests;

for my $test (@tests) {
    is_deeply
        two_sum($test->[INPUT], $test->[TARGET]),
        $test->[EXPECTED];
}

sub two_sum {
    my ($input, $target) = @_;

    my $got;

    OUTER:
    for my $i (0 .. $#$input - 1) {
        next OUTER if $input->[$i] > $target;

        INNER:
        for my $j ($i + 1 .. $#$input) {
            next INNER if $input->[$j] > $target;

            if ($input->[$i] + $input->[$j] == $target) {
                $got = [$i, $j];
                last OUTER;
            }
        }
    }

    return $got;
}