Merge pull request #203 from domix80/problem_010

Feat: Project Euler Problem 10

Author: StepfenShawn

project_euler/problem_010/sol1.rb

@@ -0,0 +1,42 @@
+#Project Euler Problem 10:  https://projecteuler.net/problem=10
+#Summation of primes
+#The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
+#Find the sum of all the primes below two million.
+#References:  https://en.wikipedia.org/wiki/Prime_number
+def is_prime?(number)   
+    value = true
+    if number > 1 and number < 4
+        # 2 and 3 are primes
+        value = true
+    elsif number < 2 or number % 2 == 0 or number % 3 == 0
+    # Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
+        value = false
+    end
+    end_range = (Math.sqrt(number) + 1).to_i
+    # All primes number are in format of 6k +/- 1
+    for i in (5..end_range).step(6)
+        if number % i == 0 or number % (i + 2) == 0
+            value = false
+        end
+    end
+    result = value
+end
+
+def solution(max_total = 2000000)
+  sum = 1
+  num = 2
+  value = 1
+  while num < max_total and value < max_total
+    if is_prime?(num)
+      value += num
+      if value < max_total
+        sum = value
+      end
+    end
+    num += 1
+  end
+  result = sum
+end
+
+answer = solution()
+p answer