Add code from group

solutions/solution-1.rb

@@ -0,0 +1,8 @@
+def solution_1(max)
+  sum = 0
+  (1...max).each do  |number|
+    sum += number if number % 3 == 0|| number % 5 == 0
+  end
+
+  sum
+end

solutions/solution-15.rb

@@ -0,0 +1,38 @@
+class Solution15
+  attr_reader :solution
+  def initialize(size)
+    @size = size
+    @grid = Array.new(size + 1){ Array.new(size + 1, 0) }
+
+    @solution = traverse(0,0)
+  end
+
+  def traverse(x, y)
+    paths = 0
+
+    if @size - x == 0 || @size - y == 0
+      @grid[x][y] = 1
+      return 1
+    end
+
+    if @grid[x][y] == 0
+      paths += traverse(x + 1, y) if x < @size
+      paths += traverse(x, y + 1) if y < @size
+
+      @grid[x][y] = paths
+      @grid[y][x] = paths
+    end
+
+    @grid[x][y]
+  end
+
+  def traverse2(x, y)
+    paths = 0
+    paths += traverse(x + 1, y) if x < @size
+    paths += traverse(x, y + 1) if y < @size
+
+    return 1 if x == @size && y == @size
+
+    return paths
+  end
+end

solutions/solution-2.rb

@@ -0,0 +1,12 @@
+def solution_2(max)
+  sum = 0
+
+  i = j = 1
+
+  while(j <= max)
+    i, j = j, i + j
+    sum += i if i.even?
+  end
+
+  sum
+end

solutions/solution-3.rb

@@ -0,0 +1,4 @@
+require 'prime'
+def solution_3(number)
+  Prime.prime_division(number).last[0]
+end

solutions/solution-4.rb

@@ -0,0 +1,20 @@
+def solution_4(digits)
+  min = min(digits)
+  max = max(digits)
+
+  (min..max)
+    .to_a
+    .map { |i| (min..max).to_a.map { |j| i * j } }
+    .flatten(1)
+    .select { |i| i.to_s == i.to_s.reverse }
+    .sort
+    .last
+end
+
+def min(digits)
+  ("1" + "0" * (digits - 1)).to_i
+end
+
+def max(digits)
+  ("1" + "0" * (digits)).to_i - 1
+end

solutions/solution-5.rb

@@ -0,0 +1,3 @@
+def solution_5(max)
+  (1..max).inject(1) { |lcm, n| lcm.lcm(n) }
+end

solutions/solution-8.rb

@@ -0,0 +1,33 @@
+def solution_8(length)
+  number = "73167176531330624919225119674426574742355349194934
+96983520312774506326239578318016984801869478851843
+85861560789112949495459501737958331952853208805511
+12540698747158523863050715693290963295227443043557
+66896648950445244523161731856403098711121722383113
+62229893423380308135336276614282806444486645238749
+30358907296290491560440772390713810515859307960866
+70172427121883998797908792274921901699720888093776
+65727333001053367881220235421809751254540594752243
+52584907711670556013604839586446706324415722155397
+53697817977846174064955149290862569321978468622482
+83972241375657056057490261407972968652414535100474
+82166370484403199890008895243450658541227588666881
+16427171479924442928230863465674813919123162824586
+17866458359124566529476545682848912883142607690042
+24219022671055626321111109370544217506941658960408
+07198403850962455444362981230987879927244284909188
+84580156166097919133875499200524063689912560717606
+05886116467109405077541002256983155200055935729725
+71636269561882670428252483600823257530420752963450".gsub(/\n/, '')
+  greatest = 0
+
+  number.split(//).each_with_index do |value, i|
+    if i >= length
+      current = ((i - length + 1)..i).map { |i| number[i].to_i }.reduce(1, :*)
+
+      greatest = current if current > greatest
+    end
+  end
+
+  return greatest
+end

spec/problem-1.rb

@@ -0,0 +1,12 @@
+require_relative 'spec_helper'
+require_relative '../solutions/solution-1'
+
+describe 'Multiples of 3 and 5' do
+  it 'works for the given example' do
+    expect(solution_1(10)).to eq(23)
+  end
+
+  it 'works for the known answer' do
+    expect(solution_1(1000)).to eq(233168)
+  end
+end