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darcnite3000's solution

to Pascal's Triangle in the CoffeeScript Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Compute Pascal's triangle up to a given number of rows.

In Pascal's Triangle each number is computed by adding the numbers to the right and left of the current position in the previous row.

    1
   1 1
  1 2 1
 1 3 3 1
1 4 6 4 1
# ... etc

Refer to the Exercism CoffeScript page for getting started with CoffeeScript.

In order to run the test, you can run the test file from the exercise directory:

jasmine-node --coffee .

Source

Pascal's Triangle at Wolfram Math World http://mathworld.wolfram.com/PascalsTriangle.html

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

pascal-triangle-spec.coffee

Pascal = require './example.coffee'

describe 'Pascal', ->
  it 'with one row', ->
    arr = new Pascal(1)
    expect(arr.array).toEqual [[1]]

  xit 'with two rows', ->
    arr = new Pascal(2)
    expect(arr.array).toEqual [[1], [1,1]]

  xit 'with three rows', ->
    arr = new Pascal(3)
    expect(arr.array).toEqual [[1], [1,1], [1,2,1]]

  xit 'with four rows', ->
    arr = new Pascal(4)
    expect(arr.array).toEqual [[1], [1,1], [1,2,1], [1,3,3,1]]

  xit 'with five rows', ->
    arr = new Pascal(5)
    expect(arr.array).toEqual [[1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]

  xit 'should equal 20th row', ->
    arr = new Pascal(20)
    expect(arr.array[19]).toEqual [1, 19, 171, 969, 3876, 11628, 27132, 50388, 75582, 92378, 92378, 75582, 50388, 27132, 11628, 3876, 969, 171, 19, 1]
module.exports = class Triangle
  constructor: (rows = 1)->
    @array = generatePascals rows
  generatePascals = (rows)->
    lastRow = generatePascalRow(lastRow) for i in [0...rows]
  generatePascalRow = (lastRow = [])->
    getPascal(lastRow[i-1], lastRow[i]) for i in [0..lastRow.length]
  getPascal = (a = 0, b = 0)-> (a+b) || 1

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