Add largest-series-product exercise (#153)

config.json

@@ -371,6 +371,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "largest-series-product",
+        "name": "Largest Series Product",
+        "uuid": "30b8f3f3-ccb1-485f-90b9-d0d81a084167",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "matching-brackets",
         "name": "Matching Brackets",

exercises/practice/largest-series-product/.docs/instructions.md

@@ -0,0 +1,26 @@
+# Instructions
+
+Your task is to look for patterns in the long sequence of digits in the encrypted signal.
+
+The technique you're going to use here is called the largest series product.
+
+Let's define a few terms, first.
+
+- **input**: the sequence of digits that you need to analyze
+- **series**: a sequence of adjacent digits (those that are next to each other) that is contained within the input
+- **span**: how many digits long each series is
+- **product**: what you get when you multiply numbers together
+
+Let's work through an example, with the input `"63915"`.
+
+- To form a series, take adjacent digits in the original input.
+- If you are working with a span of `3`, there will be three possible series:
+  - `"639"`
+  - `"391"`
+  - `"915"`
+- Then we need to calculate the product of each series:
+  - The product of the series `"639"` is 162 (`6 × 3 × 9 = 162`)
+  - The product of the series `"391"` is 27 (`3 × 9 × 1 = 27`)
+  - The product of the series `"915"` is 45 (`9 × 1 × 5 = 45`)
+- 162 is bigger than both 27 and 45, so the largest series product of `"63915"` is from the series `"639"`.
+  So the answer is **162**.

exercises/practice/largest-series-product/.docs/introduction.md

@@ -0,0 +1,5 @@
+# Introduction
+
+You work for a government agency that has intercepted a series of encrypted communication signals from a group of bank robbers.
+The signals contain a long sequence of digits.
+Your team needs to use various digital signal processing techniques to analyze the signals and identify any patterns that may indicate the planning of a heist.

exercises/practice/largest-series-product/.meta/Example.roc

@@ -0,0 +1,24 @@
+module [largestProduct]
+
+largestProduct : Str, U64 -> Result U64 [SpanWasTooLarge, InvalidDigit]
+largestProduct = \digits, span ->
+    if span == 0 then
+        Ok 1
+        else
+
+    chars = digits |> Str.toUtf8
+    if List.len chars < span then
+        Err SpanWasTooLarge
+    else if chars |> List.any \char -> char < '0' || char > '9' then
+        Err InvalidDigit
+        else
+
+    List.range { start: At 0, end: At (List.len chars - span) }
+    |> List.map \startIndex ->
+        chars
+        |> List.sublist { start: startIndex, len: span }
+        |> List.walk 1 \product, char ->
+            product * (char - '0' |> Num.toU64)
+    |> List.max
+    |> Result.onErr \ListWasEmpty -> crash "Unreachable: the list cannot be empty here"
+

exercises/practice/largest-series-product/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "LargestSeriesProduct.roc"
+    ],
+    "test": [
+      "largest-series-product-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.",
+  "source": "A variation on Problem 8 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=8"
+}

exercises/practice/largest-series-product/.meta/template.j2

@@ -0,0 +1,19 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+{{ macros.header() }}
+
+import {{ exercise | to_pascal }} exposing [{{ cases[0]["property"] | to_camel }}]
+
+{% for case in cases -%}
+# {{ case["description"] }}
+expect
+    digits = {{ case["input"]["digits"] | to_roc }}
+    result = digits |> {{ case["property"] | to_camel }} {{ case["input"]["span"] | to_roc }}
+    {%- if case["expected"]["error"] %}
+    result |> Result.isErr
+    {%- else %}
+    expected = Ok {{ case["expected"] | to_roc }}
+    result == expected
+    {%- endif %}
+
+{% endfor %}

exercises/practice/largest-series-product/.meta/tests.toml

@@ -0,0 +1,61 @@
+# 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.
+
+[7c82f8b7-e347-48ee-8a22-f672323324d4]
+description = "finds the largest product if span equals length"
+
+[88523f65-21ba-4458-a76a-b4aaf6e4cb5e]
+description = "can find the largest product of 2 with numbers in order"
+
+[f1376b48-1157-419d-92c2-1d7e36a70b8a]
+description = "can find the largest product of 2"
+
+[46356a67-7e02-489e-8fea-321c2fa7b4a4]
+description = "can find the largest product of 3 with numbers in order"
+
+[a2dcb54b-2b8f-4993-92dd-5ce56dece64a]
+description = "can find the largest product of 3"
+
+[673210a3-33cd-4708-940b-c482d7a88f9d]
+description = "can find the largest product of 5 with numbers in order"
+
+[02acd5a6-3bbf-46df-8282-8b313a80a7c9]
+description = "can get the largest product of a big number"
+
+[76dcc407-21e9-424c-a98e-609f269622b5]
+description = "reports zero if the only digits are zero"
+
+[6ef0df9f-52d4-4a5d-b210-f6fae5f20e19]
+description = "reports zero if all spans include zero"
+
+[5d81aaf7-4f67-4125-bf33-11493cc7eab7]
+description = "rejects span longer than string length"
+
+[06bc8b90-0c51-4c54-ac22-3ec3893a079e]
+description = "reports 1 for empty string and empty product (0 span)"
+
+[3ec0d92e-f2e2-4090-a380-70afee02f4c0]
+description = "reports 1 for nonempty string and empty product (0 span)"
+
+[6d96c691-4374-4404-80ee-2ea8f3613dd4]
+description = "rejects empty string and nonzero span"
+
+[7a38f2d6-3c35-45f6-8d6f-12e6e32d4d74]
+description = "rejects invalid character in digits"
+
+[5fe3c0e5-a945-49f2-b584-f0814b4dd1ef]
+description = "rejects negative span"
+include = false
+
+[c859f34a-9bfe-4897-9c2f-6d7f8598e7f0]
+description = "rejects negative span"
+reimplements = "5fe3c0e5-a945-49f2-b584-f0814b4dd1ef"
+include = false

exercises/practice/largest-series-product/LargestSeriesProduct.roc

@@ -0,0 +1,5 @@
+module [largestProduct]
+
+largestProduct : Str, U64 -> Result U64 _
+largestProduct = \digits, span ->
+    crash "Please implement the 'largestProduct' function"

exercises/practice/largest-series-product/largest-series-product-test.roc

@@ -0,0 +1,107 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/largest-series-product/canonical-data.json
+# File last updated on 2024-10-13
+app [main] {
+    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.15.0/SlwdbJ-3GR7uBWQo6zlmYWNYOxnvo8r6YABXD-45UOw.tar.br",
+}
+
+main =
+    Task.ok {}
+
+import LargestSeriesProduct exposing [largestProduct]
+
+# finds the largest product if span equals length
+expect
+    digits = "29"
+    result = digits |> largestProduct 2
+    expected = Ok 18
+    result == expected
+
+# can find the largest product of 2 with numbers in order
+expect
+    digits = "0123456789"
+    result = digits |> largestProduct 2
+    expected = Ok 72
+    result == expected
+
+# can find the largest product of 2
+expect
+    digits = "576802143"
+    result = digits |> largestProduct 2
+    expected = Ok 48
+    result == expected
+
+# can find the largest product of 3 with numbers in order
+expect
+    digits = "0123456789"
+    result = digits |> largestProduct 3
+    expected = Ok 504
+    result == expected
+
+# can find the largest product of 3
+expect
+    digits = "1027839564"
+    result = digits |> largestProduct 3
+    expected = Ok 270
+    result == expected
+
+# can find the largest product of 5 with numbers in order
+expect
+    digits = "0123456789"
+    result = digits |> largestProduct 5
+    expected = Ok 15120
+    result == expected
+
+# can get the largest product of a big number
+expect
+    digits = "73167176531330624919225119674426574742355349194934"
+    result = digits |> largestProduct 6
+    expected = Ok 23520
+    result == expected
+
+# reports zero if the only digits are zero
+expect
+    digits = "0000"
+    result = digits |> largestProduct 2
+    expected = Ok 0
+    result == expected
+
+# reports zero if all spans include zero
+expect
+    digits = "99099"
+    result = digits |> largestProduct 3
+    expected = Ok 0
+    result == expected
+
+# rejects span longer than string length
+expect
+    digits = "123"
+    result = digits |> largestProduct 4
+    result |> Result.isErr
+
+# reports 1 for empty string and empty product (0 span)
+expect
+    digits = ""
+    result = digits |> largestProduct 0
+    expected = Ok 1
+    result == expected
+
+# reports 1 for nonempty string and empty product (0 span)
+expect
+    digits = "123"
+    result = digits |> largestProduct 0
+    expected = Ok 1
+    result == expected
+
+# rejects empty string and nonzero span
+expect
+    digits = ""
+    result = digits |> largestProduct 1
+    result |> Result.isErr
+
+# rejects invalid character in digits
+expect
+    digits = "1234a5"
+    result = digits |> largestProduct 2
+    result |> Result.isErr
+