Add largest-series-product (#328)

Author: BNAndras

config.json

@@ -558,6 +558,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "largest-series-product",
+        "name": "Largest Series Product",
+        "uuid": "9ae397e6-da06-433a-b4dc-118c01b73a8a",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "nth-prime",
         "name": "Nth Prime",

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/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "largest-series-product.coffee"
+    ],
+    "test": [
+      "largest-series-product.spec.coffee"
+    ],
+    "example": [
+      ".meta/example.coffee"
+    ]
+  },
+  "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/example.coffee

@@ -0,0 +1,19 @@
+class LargestSeriesProduct
+  @largestProduct: (digits, span) ->
+    if span < 0
+      throw new Error 'span must not be negative'
+    if span > digits.length
+      throw new Error 'span must be smaller than string length'
+    if digits.match(/[^0-9]/)
+      throw new Error 'digits input must only contain digits'
+
+    max = 0
+    for i in [0...digits.length - span + 1]
+      product = 1
+      for j in [0...span]
+        product *= Number digits[i + j]
+      if product > max
+        max = product
+    max
+
+module.exports = LargestSeriesProduct

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

@@ -0,0 +1,60 @@
+# 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"

exercises/practice/largest-series-product/largest-series-product.coffee

@@ -0,0 +1,4 @@
+class LargestSeriesProduct
+  @largestProduct: (digits, span) ->
+
+module.exports = LargestSeriesProduct

exercises/practice/largest-series-product/largest-series-product.spec.coffee

@@ -0,0 +1,66 @@
+Lsp = require './largest-series-product'
+
+describe 'Largest Series Product', ->
+  it 'finds the largest product if span equals length', ->
+    result = Lsp.largestProduct '29', 2
+    expect(result).toEqual 18
+
+  xit 'can find the largest product of 2 with numbers in order', ->
+    result = Lsp.largestProduct '0123456789', 2
+    expect(result).toEqual 72
+
+  xit 'can find the largest product of 2', ->
+    result = Lsp.largestProduct '576802143', 2
+    expect(result).toEqual 48
+  
+  xit 'can find the largest product of 3 with numbers in order', ->
+    result = Lsp.largestProduct '0123456789', 3
+    expect(result).toEqual 504
+
+  xit 'can find the largest product of 3', ->
+    result = Lsp.largestProduct '1027839564', 3
+    expect(result).toEqual 270
+
+  xit 'can find the largest product of 5 with numbers in order', ->
+    result = Lsp.largestProduct '0123456789', 5
+    expect(result).toEqual 15120
+  
+  xit 'can get the largest product of a big number', ->
+    result = Lsp.largestProduct '73167176531330624919225119674426574742355349194934', 6
+    expect(result).toEqual 23520
+
+  xit 'reports zero if the only digits are zero', ->
+    result = Lsp.largestProduct '0000', 2
+    expect(result).toEqual 0
+
+  xit 'reports zero if all spans include zero', ->
+    result = Lsp.largestProduct '99099', 3
+    expect(result).toEqual 0
+
+  xit 'rejects span longer than string length', ->
+    expect ->
+      Lsp.largestProduct '123', 4
+    .toThrow new Error 'span must be smaller than string length'
+
+  xit 'reports 1 for empty string and empty product (0 span)', ->
+    result = Lsp.largestProduct '', 0
+    expect(result).toEqual 1
+
+  xit 'reports 1 for nonempty string and empty product (0 span)', ->
+    result = Lsp.largestProduct '123', 0
+    expect(result).toEqual 1
+
+  xit 'rejects empty string and nonzero span', ->
+    expect ->
+      Lsp.largestProduct '', 1
+    .toThrow new Error 'span must be smaller than string length'
+
+  xit 'rejects invalid character in digits', ->
+    expect ->
+      Lsp.largestProduct '1234a5', 2
+    .toThrow new Error 'digits input must only contain digits'
+
+  xit 'rejects negative span', ->
+    expect ->
+      Lsp.largestProduct '12345', -1
+    .toThrow new Error 'span must not be negative'