Dev Prework

problem03.rb

@@ -0,0 +1,15 @@
+def larg_prim num
+	prime_factor = 0
+	testNum = 2 
+	while testNum <= num
+		if num % testNum == 0
+			prime_factor = testNum
+			num /= testNum
+		else
+			testNum +=1
+		end
+	end
+	return prime_factor
+end
+
+puts larg_prim(600851475143)

problem05.rb

@@ -0,0 +1,39 @@
+def lcm max_num
+	# Get a list of all prime factors.
+	prime_arr = []
+	(2..max_num).each do |x|
+		if is_prime? x
+			prime_arr << x
+		end
+	end
+
+	# Find the LCM
+	factors_arr = prime_arr
+	prime_arr.each do |x|
+		counter = 2
+		while x <= Math.sqrt(max_num)
+			if x ** counter <= max_num
+				factors_arr.push(x ** counter)
+				index = factors_arr.find_index(x ** (counter-1))
+				factors_arr.delete_at(index)
+			else
+				break
+			end
+			counter += 1
+		end
+	end
+
+	return factors_arr.compact.inject(:*)
+end
+
+def is_prime? num
+	testNum = 2
+	while testNum < num
+		if num % testNum == 0
+			return false
+		else
+			testNum += 1
+		end
+	end
+	return true
+end

problem08.rb

@@ -0,0 +1,16 @@
+def greatest5(num)
+	digits = num.to_s.chars.map(&:to_i)
+	i = 0
+	greatest_prod = 0
+	while (i+4) < digits.length
+		product = (digits[i..i+4].inject(:*))
+		if product > greatest_prod
+			greatest_prod = product
+		end
+		i += 1
+	end
+
+	return greatest_prod
+end
+
+puts greatest5 (7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450)