Project Euler: Problems 3, 5, 8

problem03.rb

@@ -0,0 +1,13 @@
+# Project Euler: What is the largest prime factor of the number 600851475143?
+
+def largest_prime_factor(number)
+	for i in (2...number)
+		if number % i == 0
+			factor = number/i
+			return largest_prime_factor(factor)
+		end
+	end
+	return number
+end
+
+puts "Largest Prime Factor: #{largest_prime_factor(600851475143)}"

problem05.rb

@@ -0,0 +1,34 @@
+# Project Euler: What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
+def get_prime_factors(number)
+    primes = []
+    for i in (2...number)
+        if number % i ==0
+            while number % i == 0
+                number = number / i
+                primes << i
+            end
+        end
+    end
+    primes = [1, number] if primes.empty?
+    return primes
+end
+
+def least_common_multiple(number)
+    factors_to_frequency = Hash.new
+    for i in (1..number)
+        prime_factors = get_prime_factors(i)
+        for number in prime_factors
+           factors_to_frequency[number] ||= prime_factors.count(number)
+           factors_to_frequency[number] = prime_factors.count(number) if prime_factors.count(number) > factors_to_frequency[number]
+        end
+    end
+
+    total = 1
+    factors_to_frequency.each do |key, value|
+        total = total * key ** value
+    end
+
+    return total
+end
+
+puts "Least Common Multiple: #{least_common_multiple(20)}"

problem08.rb

@@ -0,0 +1,18 @@
+# Project Euler: Find the greatest product of five consecutive digits in the 1000-digit number.
+
+my_number = 7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450
+chunk_size = 5
+
+my_number = my_number.to_s
+start_index = 0
+max_product = 0
+while (start_index < my_number.size)
+    chunk = my_number[start_index, chunk_size]
+    start_index += 1
+
+    product = chunk.split("").inject(1) { |total, n| total * n.to_i }
+
+    max_product = product if product > max_product
+end
+
+puts "Max Product: #{max_product}"