JaeHyoLee's solution to Pascal's Triangle on the Lua track

Instructions

Test suite

Solution

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.

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.

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.

pascals-triangle_spec.lua

local Triangle = require('pascals-triangle')

describe('pascals-triangle', function()
  it('should generate a triangle with one row', function()
    assert.same({ { 1 } }, Triangle(1).rows)
  end)

  it('should generate a triangle with two rows', function()
    assert.same({ { 1 }, { 1, 1 } }, Triangle(2).rows)
  end)

  it('should generate a triangle with three rows', function()
    assert.same({ { 1 }, { 1, 1 }, { 1, 2, 1 } }, Triangle(3).rows)
  end)

  it('should allow the last row to be accessed directly', function()
    assert.same({ 1, 2, 1 }, Triangle(3).last_row)
  end)

  it('should generate the fourth row correctly', function()
    assert.same({ 1, 3, 3, 1 }, Triangle(4).last_row)
  end)

  it('should generate the fifth row correctly', function()
    assert.same({ 1, 4, 6, 4, 1 }, Triangle(5).last_row)
  end)

  it('should generate the twentieth row correctly', function()
    local twentieth = { 1, 19, 171, 969, 3876, 11628, 27132, 50388, 75582, 92378, 92378, 75582, 50388, 27132, 11628, 3876, 969, 171, 19, 1 }
    assert.same(twentieth, Triangle(20).last_row)
  end)
end)

return function (nth)
  local rows = {}
  for i = 1, nth do
    local elements = {1}
    for j = 2, i do
      elements[j] = rows[i-1][j-1] + (rows[i-1][j] or 0)
    end
    table.insert(rows,elements)
  end

  return {
    rows = rows,
    last_row = rows[nth]
  }
end

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JaeHyoLee's solution

to Pascal's Triangle in the Lua Track