26 December 2025

Challenge 353

The Maximum Coupon

• Task 1: Max Words
• Task 2: Validate Coupon

Task 1: Max Words

Submitted by: Mohammad Sajid Anwar

---

You are given an array of sentences.

Write a script to return the maximum number of words that appear in a single sentence.

Example 1

Input: @sentences = ("Hello world", "This is a test", "Perl is great")
Output: 4

Example 2

Input: @sentences = ("Single")
Output: 1

Example 3

Input: @sentences = ("Short", "This sentence has seven words in total", "A B C",
                     "Just four words here")
Output: 7

Example 4

Input: @sentences = ("One", "Two parts", "Three part phrase", "")
Output: 3

Example 5

Input: @sentences = ("The quick brown fox jumps over the lazy dog", "A",
                     "She sells seashells by the seashore",
                     "To be or not to be that is the question")
Output: 10

---

Solution

Perl

Using the regex Special Escape \w to identify words. Global Matching in list context finds all words. Converted to scalar context this yields the number of words.

use strict;
use warnings;
use List::Util 'max';

sub max_words {
    max map scalar(() = /\w+/g), @_;
}

See the full solution to task 1.

J

The J implementation is similar: use cutopen to split each sentence into words, count them and find the maximum thereof.

MaxWords =: >./ @ (# S:1) @ (cutopen L:0)

echo MaxWords 'Hello world'; 'This is a test'; 'Perl is great'

See the full solution.

Task 2: Validate Coupon

Submitted by: Mohammad Sajid Anwar

---

You are given three arrays, @codes, @names and @status.

Write a script to validate codes in the given array.

A code is valid when the following conditions are true:

• codes[i] is non-empty and consists only of alphanumeric characters (a-z, A-Z, 0-9) and underscores (_).
• names[i] is one of the following four categories: "electronics", "grocery", "pharmacy", "restaurant".
• status[i] is true.

Return an array of booleans indicating validity: output[i] is true if and only if codes[i], names[i] and status[i] are all valid.

Example 1

Input: @codes  = ("A123", "B_456", "C789", "D@1", "E123")
       @names  = ("electronics", "restaurant", "electronics", "pharmacy",
                  "grocery")
       @status = ("true", "false", "true", "true", "true")
Output: (true, false, true, false, true)

Example 2

Input: @codes  = ("Z_9", "AB_12", "G01", "X99", "test")
       @names  = ("pharmacy", "electronics", "grocery", "electronics", "unknown")
       @status = ("true", "true", "false", "true", "true")
Output: (true, true, false, true, false)

Example 3

Input: @codes  = ("_123", "123", "", "Coupon_A", "Alpha")
       @names  = ("restaurant", "electronics", "electronics", "pharmacy",
                  "grocery")
       @status = ("true", "true", "false", "true", "true")
Output: (true, true, false, true, true)

Example 4

Input: @codes  = ("ITEM_1", "ITEM_2", "ITEM_3", "ITEM_4")
       @names  = ("electronics", "electronics", "grocery", "grocery")
       @status = ("true", "true", "true", "true")
Output: (true, true, true, true)

Example 5

Input: @codes  = ("CAFE_X", "ELEC_100", "FOOD_1", "DRUG_A", "ELEC_99")
       @names  = ("restaurant", "electronics", "grocery", "pharmacy",
                  "electronics")
       @status = ("true", "true", "true", "true", "false")
Output: (true, true, true, true, false)

---

Solution

Perl

Zip codes, names and status and check for each triple whether the code consist of word characters \w only, the name is contained in the list of categories and the status equals 'true'.

use strict;
use warnings;

sub validate_coupon {
    (\my %cat)->@{qw(electronics grocery pharmacy restaurant)} = ();
    map {
        0 + ($_->[0] =~ /^\w+$/ && exists $cat{$_->[1]} && $_->[2] eq 'true')
    } zip @_;
}

See the full solution to task 2.

J

Use '^\w+$'&rxeq&.> y to check the codes, cat&(e.~) y to check the categories and (<'true')&(e.~) y to check the status. Checks are combined with bitwise logical AND.

require 'regex'
cat =: 'electronics'; 'grocery'; 'pharmacy'; 'restaurant'
ValidCoupon =: (<'true')&(e.~)@(2&{) *. cat&(e.~)@(1&{) *. >@('^\w+$'&rxeq&.>)@(0&{)

echo ValidCoupon ('A123'; 'B_456'; 'C789'; 'D@1'; 'E123'), ('electronics'; 'restaurant'; 'electronics'; 'pharmacy'; 'grocery'),: ('true'; 'false'; 'true'; 'true'; 'true')

See the full solution.