From 51924983a23e0055d8d73f729985a01668b551f3 Mon Sep 17 00:00:00 2001 From: Glenn Jackman Date: Wed, 8 Apr 2026 16:39:44 -0400 Subject: [PATCH] Add pascals-triangle --- bin/add-practice-exercise | 4 +- config.json | 8 ++ exercises/practice/pascals-triangle/.busted | 5 ++ .../pascals-triangle/.docs/instructions.md | 35 +++++++++ .../pascals-triangle/.docs/introduction.md | 22 ++++++ .../pascals-triangle/.meta/config.json | 19 +++++ .../pascals-triangle/.meta/example.moon | 14 ++++ .../.meta/spec_generator.moon | 25 ++++++ .../pascals-triangle/.meta/tests.toml | 34 ++++++++ .../pascals-triangle/pascals_triangle.moon | 4 + .../pascals_triangle_spec.moon | 78 +++++++++++++++++++ 11 files changed, 247 insertions(+), 1 deletion(-) create mode 100644 exercises/practice/pascals-triangle/.busted create mode 100644 exercises/practice/pascals-triangle/.docs/instructions.md create mode 100644 exercises/practice/pascals-triangle/.docs/introduction.md create mode 100644 exercises/practice/pascals-triangle/.meta/config.json create mode 100644 exercises/practice/pascals-triangle/.meta/example.moon create mode 100644 exercises/practice/pascals-triangle/.meta/spec_generator.moon create mode 100644 exercises/practice/pascals-triangle/.meta/tests.toml create mode 100644 exercises/practice/pascals-triangle/pascals_triangle.moon create mode 100644 exercises/practice/pascals-triangle/pascals_triangle_spec.moon diff --git a/bin/add-practice-exercise b/bin/add-practice-exercise index b692d19..14a730e 100755 --- a/bin/add-practice-exercise +++ b/bin/add-practice-exercise @@ -91,7 +91,9 @@ curl -s -o "canonical-data/${slug}.json" "$github" camel_slug=$(perl -pe 's/(?:^|-)([a-z])/\u$1/g' <<< "$slug") -cp -v exercises/shared/templates/spec_generator.moon exercises/practice/${slug}/.meta/spec_generator.moon +template=$(< exercises/shared/templates/spec_generator.moon) +template=${template//'${camel_slug}'/"${camel_slug}"} +echo "$template" > exercises/practice/${slug}/.meta/spec_generator.moon cat << NEXT_STEPS diff --git a/config.json b/config.json index 9af302a..45d5020 100644 --- a/config.json +++ b/config.json @@ -490,6 +490,14 @@ "prerequisites": [], "difficulty": 4 }, + { + "slug": "pascals-triangle", + "name": "Pascal's Triangle", + "uuid": "f64601d6-c1fb-4582-8963-fe5510fb2d97", + "practices": [], + "prerequisites": [], + "difficulty": 4 + }, { "slug": "prism", "name": "Prism", diff --git a/exercises/practice/pascals-triangle/.busted b/exercises/practice/pascals-triangle/.busted new file mode 100644 index 0000000..86b84e7 --- /dev/null +++ b/exercises/practice/pascals-triangle/.busted @@ -0,0 +1,5 @@ +return { + default = { + ROOT = { '.' } + } +} diff --git a/exercises/practice/pascals-triangle/.docs/instructions.md b/exercises/practice/pascals-triangle/.docs/instructions.md new file mode 100644 index 0000000..0f58f00 --- /dev/null +++ b/exercises/practice/pascals-triangle/.docs/instructions.md @@ -0,0 +1,35 @@ +# Instructions + +Your task is to output the first N rows of Pascal's triangle. + +[Pascal's triangle][wikipedia] is a triangular array of positive integers. + +In Pascal's triangle, the number of values in a row is equal to its row number (which starts at one). +Therefore, the first row has one value, the second row has two values, and so on. + +The first (topmost) row has a single value: `1`. +Subsequent rows' values are computed by adding the numbers directly to the right and left of the current position in the previous row. + +If the previous row does _not_ have a value to the left or right of the current position (which only happens for the leftmost and rightmost positions), treat that position's value as zero (effectively "ignoring" it in the summation). + +## Example + +Let's look at the first 5 rows of Pascal's Triangle: + +```text + 1 + 1 1 + 1 2 1 + 1 3 3 1 +1 4 6 4 1 +``` + +The topmost row has one value, which is `1`. + +The leftmost and rightmost values have only one preceding position to consider, which is the position to its right respectively to its left. +With the topmost value being `1`, it follows from this that all the leftmost and rightmost values are also `1`. + +The other values all have two positions to consider. +For example, the fifth row's (`1 4 6 4 1`) middle value is `6`, as the values to its left and right in the preceding row are `3` and `3`: + +[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle diff --git a/exercises/practice/pascals-triangle/.docs/introduction.md b/exercises/practice/pascals-triangle/.docs/introduction.md new file mode 100644 index 0000000..eab454e --- /dev/null +++ b/exercises/practice/pascals-triangle/.docs/introduction.md @@ -0,0 +1,22 @@ +# Introduction + +With the weather being great, you're not looking forward to spending an hour in a classroom. +Annoyed, you enter the class room, where you notice a strangely satisfying triangle shape on the blackboard. +Whilst waiting for your math teacher to arrive, you can't help but notice some patterns in the triangle: the outer values are all ones, each subsequent row has one more value than its previous row and the triangle is symmetrical. +Weird! + +Not long after you sit down, your teacher enters the room and explains that this triangle is the famous [Pascal's triangle][wikipedia]. + +Over the next hour, your teacher reveals some amazing things hidden in this triangle: + +- It can be used to compute how many ways you can pick K elements from N values. +- It contains the Fibonacci sequence. +- If you color odd and even numbers differently, you get a beautiful pattern called the [Sierpiński triangle][wikipedia-sierpinski-triangle]. + +The teacher implores you and your classmates to look up other uses, and assures you that there are lots more! +At that moment, the school bell rings. +You realize that for the past hour, you were completely absorbed in learning about Pascal's triangle. +You quickly grab your laptop from your bag and go outside, ready to enjoy both the sunshine _and_ the wonders of Pascal's triangle. + +[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle +[wikipedia-sierpinski-triangle]: https://en.wikipedia.org/wiki/Sierpi%C5%84ski_triangle diff --git a/exercises/practice/pascals-triangle/.meta/config.json b/exercises/practice/pascals-triangle/.meta/config.json new file mode 100644 index 0000000..0a13829 --- /dev/null +++ b/exercises/practice/pascals-triangle/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "glennj" + ], + "files": { + "solution": [ + "pascals_triangle.moon" + ], + "test": [ + "pascals_triangle_spec.moon" + ], + "example": [ + ".meta/example.moon" + ] + }, + "blurb": "Compute Pascal's triangle up to a given number of rows.", + "source": "Pascal's Triangle at Wolfram Math World", + "source_url": "https://www.wolframalpha.com/input/?i=Pascal%27s+triangle" +} diff --git a/exercises/practice/pascals-triangle/.meta/example.moon b/exercises/practice/pascals-triangle/.meta/example.moon new file mode 100644 index 0000000..bb73b77 --- /dev/null +++ b/exercises/practice/pascals-triangle/.meta/example.moon @@ -0,0 +1,14 @@ +FACTORIALS = {[0]: 1, [1]: 1} + +factorial = (n) -> + if not FACTORIALS[n] + FACTORIALS[n] = n * factorial(n - 1) + FACTORIALS[n] + +choose = (n, k) -> + factorial(n) // factorial(k) // factorial(n - k) + +{ + rows: (n) -> + [ [choose(i, j) for j = 0, i] for i = 0, n - 1] +} diff --git a/exercises/practice/pascals-triangle/.meta/spec_generator.moon b/exercises/practice/pascals-triangle/.meta/spec_generator.moon new file mode 100644 index 0000000..b6ef255 --- /dev/null +++ b/exercises/practice/pascals-triangle/.meta/spec_generator.moon @@ -0,0 +1,25 @@ +int_list = (list) -> "{#{table.concat list, ', '}}" + +int_lists = (lists, level) -> + if #lists == 0 + '{}' + elseif #lists == 1 + "{#{int_list lists[1]}}" + else + rows = [indent int_list(row) .. ',', level + 1 for row in *lists] + table.insert rows, 1, '{' + table.insert rows, indent '}', level + table.concat rows, '\n' + + +{ + module_name: 'PascalsTriangle', + + generate_test: (case, level) -> + lines = { + "result = PascalsTriangle.#{case.property} #{case.input.count}", + "expected = #{int_lists case.expected, level}", + "assert.are.same expected, result" + } + table.concat [indent line, level for line in *lines], '\n' +} diff --git a/exercises/practice/pascals-triangle/.meta/tests.toml b/exercises/practice/pascals-triangle/.meta/tests.toml new file mode 100644 index 0000000..2db0ee5 --- /dev/null +++ b/exercises/practice/pascals-triangle/.meta/tests.toml @@ -0,0 +1,34 @@ +# 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. + +[9920ce55-9629-46d5-85d6-4201f4a4234d] +description = "zero rows" + +[70d643ce-a46d-4e93-af58-12d88dd01f21] +description = "single row" + +[a6e5a2a2-fc9a-4b47-9f4f-ed9ad9fbe4bd] +description = "two rows" + +[97206a99-79ba-4b04-b1c5-3c0fa1e16925] +description = "three rows" + +[565a0431-c797-417c-a2c8-2935e01ce306] +description = "four rows" + +[06f9ea50-9f51-4eb2-b9a9-c00975686c27] +description = "five rows" + +[c3912965-ddb4-46a9-848e-3363e6b00b13] +description = "six rows" + +[6cb26c66-7b57-4161-962c-81ec8c99f16b] +description = "ten rows" diff --git a/exercises/practice/pascals-triangle/pascals_triangle.moon b/exercises/practice/pascals-triangle/pascals_triangle.moon new file mode 100644 index 0000000..f788d13 --- /dev/null +++ b/exercises/practice/pascals-triangle/pascals_triangle.moon @@ -0,0 +1,4 @@ +{ + rows: (n) -> + error 'Implement me' +} diff --git a/exercises/practice/pascals-triangle/pascals_triangle_spec.moon b/exercises/practice/pascals-triangle/pascals_triangle_spec.moon new file mode 100644 index 0000000..490b978 --- /dev/null +++ b/exercises/practice/pascals-triangle/pascals_triangle_spec.moon @@ -0,0 +1,78 @@ +PascalsTriangle = require 'pascals_triangle' + +describe 'pascals-triangle', -> + it 'zero rows', -> + result = PascalsTriangle.rows 0 + expected = {} + assert.are.same expected, result + + pending 'single row', -> + result = PascalsTriangle.rows 1 + expected = {{1}} + assert.are.same expected, result + + pending 'two rows', -> + result = PascalsTriangle.rows 2 + expected = { + {1}, + {1, 1}, + } + assert.are.same expected, result + + pending 'three rows', -> + result = PascalsTriangle.rows 3 + expected = { + {1}, + {1, 1}, + {1, 2, 1}, + } + assert.are.same expected, result + + pending 'four rows', -> + result = PascalsTriangle.rows 4 + expected = { + {1}, + {1, 1}, + {1, 2, 1}, + {1, 3, 3, 1}, + } + assert.are.same expected, result + + pending 'five rows', -> + result = PascalsTriangle.rows 5 + expected = { + {1}, + {1, 1}, + {1, 2, 1}, + {1, 3, 3, 1}, + {1, 4, 6, 4, 1}, + } + assert.are.same expected, result + + pending 'six rows', -> + result = PascalsTriangle.rows 6 + expected = { + {1}, + {1, 1}, + {1, 2, 1}, + {1, 3, 3, 1}, + {1, 4, 6, 4, 1}, + {1, 5, 10, 10, 5, 1}, + } + assert.are.same expected, result + + pending 'ten rows', -> + result = PascalsTriangle.rows 10 + expected = { + {1}, + {1, 1}, + {1, 2, 1}, + {1, 3, 3, 1}, + {1, 4, 6, 4, 1}, + {1, 5, 10, 10, 5, 1}, + {1, 6, 15, 20, 15, 6, 1}, + {1, 7, 21, 35, 35, 21, 7, 1}, + {1, 8, 28, 56, 70, 56, 28, 8, 1}, + {1, 9, 36, 84, 126, 126, 84, 36, 9, 1}, + } + assert.are.same expected, result