Add palindrome-products exercise (#126)

config.json

@@ -602,6 +602,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "slug": "palindrome-products",
+        "name": "Palindrome Products",
+        "uuid": "2810c41a-49c6-4db3-9afe-7f39bb2de651",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
+      },
       {
         "slug": "parallel-letter-frequency",
         "name": "Parallel Letter Frequency",

exercises/practice/palindrome-products/.docs/instructions.md

@@ -0,0 +1,36 @@
+# Instructions
+
+Detect palindrome products in a given range.
+
+A palindromic number is a number that remains the same when its digits are reversed.
+For example, `121` is a palindromic number but `112` is not.
+
+Given a range of numbers, find the largest and smallest palindromes which
+are products of two numbers within that range.
+
+Your solution should return the largest and smallest palindromes, along with the factors of each within the range.
+If the largest or smallest palindrome has more than one pair of factors within the range, then return all the pairs.
+
+## Example 1
+
+Given the range `[1, 9]` (both inclusive)...
+
+And given the list of all possible products within this range:
+`[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 15, 21, 24, 27, 20, 28, 32, 36, 25, 30, 35, 40, 45, 42, 48, 54, 49, 56, 63, 64, 72, 81]`
+
+The palindrome products are all single digit numbers (in this case):
+`[1, 2, 3, 4, 5, 6, 7, 8, 9]`
+
+The smallest palindrome product is `1`.
+Its factors are `(1, 1)`.
+The largest palindrome product is `9`.
+Its factors are `(1, 9)` and `(3, 3)`.
+
+## Example 2
+
+Given the range `[10, 99]` (both inclusive)...
+
+The smallest palindrome product is `121`.
+Its factors are `(11, 11)`.
+The largest palindrome product is `9009`.
+Its factors are `(91, 99)`.

exercises/practice/palindrome-products/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "palindrome-products.ua"
+    ],
+    "test": [
+      "tests.ua"
+    ],
+    "example": [
+      ".meta/example.ua"
+    ]
+  },
+  "blurb": "Detect palindrome products in a given range.",
+  "source": "Problem 4 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=4"
+}

exercises/practice/palindrome-products/.meta/example.ua

@@ -0,0 +1,12 @@
+IsPalindrome ← ≍⇌.°⋕
+Products! ← (
+  ⍤"invalid range"◡≥
+  ⍜(-|⇡+1)
+  ⧅≤2
+  ⊸(≡/×)
+  ≡⊂∩▽⟜:≡IsPalindrome.
+  ▽⊸(¬±⊛≡⊢)^0⍆
+)
+
+Smallest ← Products!∘
+Largest  ← Products!⇌

exercises/practice/palindrome-products/.meta/tests.toml

@@ -0,0 +1,51 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[5cff78fe-cf02-459d-85c2-ce584679f887]
+description = "find the smallest palindrome from single digit factors"
+
+[0853f82c-5fc4-44ae-be38-fadb2cced92d]
+description = "find the largest palindrome from single digit factors"
+
+[66c3b496-bdec-4103-9129-3fcb5a9063e1]
+description = "find the smallest palindrome from double digit factors"
+
+[a10682ae-530a-4e56-b89d-69664feafe53]
+description = "find the largest palindrome from double digit factors"
+
+[cecb5a35-46d1-4666-9719-fa2c3af7499d]
+description = "find the smallest palindrome from triple digit factors"
+
+[edab43e1-c35f-4ea3-8c55-2f31dddd92e5]
+description = "find the largest palindrome from triple digit factors"
+
+[4f802b5a-9d74-4026-a70f-b53ff9234e4e]
+description = "find the smallest palindrome from four digit factors"
+include = false
+
+[787525e0-a5f9-40f3-8cb2-23b52cf5d0be]
+description = "find the largest palindrome from four digit factors"
+include = false
+
+[58fb1d63-fddb-4409-ab84-a7a8e58d9ea0]
+description = "empty result for smallest if no palindrome in the range"
+
+[9de9e9da-f1d9-49a5-8bfc-3d322efbdd02]
+description = "empty result for largest if no palindrome in the range"
+
+[12e73aac-d7ee-4877-b8aa-2aa3dcdb9f8a]
+description = "error result for smallest if min is more than max"
+
+[eeeb5bff-3f47-4b1e-892f-05829277bd74]
+description = "error result for largest if min is more than max"
+
+[16481711-26c4-42e0-9180-e2e4e8b29c23]
+description = "smallest product does not use the smallest factor"

exercises/practice/palindrome-products/palindrome-products.ua

@@ -0,0 +1,7 @@
+# Find the smallest palindrome product of two numbers in a range
+# PalindromeProducts ? Min Max
+Smallest ← |2 ⊙⋅(⍤ "Please implement Smallest" 0)
+
+# Find the largest palindrome product of two numbers in a range
+# PalindromeProducts ? Min Max
+Largest ← |2 ⊙⋅(⍤ "Please implement Largest" 0)

exercises/practice/palindrome-products/tests.ua

@@ -0,0 +1,39 @@
+~ "palindrome-products.ua" ~ Largest Smallest
+
+# Find the smallest palindrome from single digit factors
+Expected ← [1_1_1]
+⍤⤙≍ Expected Smallest 1 9
+
+# Find the largest palindrome from single digit factors
+Expected ← [9_1_9 9_3_3]
+⍤⤙≍ Expected⍆ Largest 1 9
+
+# Find the smallest palindrome from double digit factors
+Expected ← [121_11_11]
+⍤⤙≍ Expected Smallest 10 99
+
+# Find the largest palindrome from double digit factors
+Expected ← [9009_91_99]
+⍤⤙≍ Expected Largest 10 99
+
+# Find the smallest palindrome from triple digit factors
+Expected ← [10201_101_101]
+⍤⤙≍ Expected Smallest 100 999
+
+# Find the largest palindrome from triple digit factors
+Expected ← [906609_913_993]
+⍤⤙≍ Expected Largest 100 999
+
+# Empty result for smallest if no palindrome in the range
+Expected ← ↯0_3[]
+⍤⤙≍ Expected Smallest 1002 1003
+
+# Empty result for largest if no palindrome in the range
+Expected ← ↯0_3[]
+⍤⤙≍ Expected Largest 15 15
+
+# Error result for smallest if min is more than max
+⍤⤙≍ "invalid range" ⍣(Smallest 10000 1)
+
+# Error result for largest if min is more than max
+⍤⤙≍ "invalid range" ⍣(Largest 2 1)