Merge pull request #204 from domix80/problem_025

Feat: Project Euler Problem 25

Author: StepfenShawn

project_euler/problem_025/sol1.rb

@@ -0,0 +1,44 @@
+#The Fibonacci sequence is defined by the recurrence relation:
+#    Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1.
+#Hence the first 12 terms will be:
+#
+#    F1 = 1
+#    F2 = 1
+#    F3 = 2
+#    F4 = 3
+#    F5 = 5
+#    F7 = 13
+#    F8 = 21
+#    F6 = 8
+#    F9 = 34
+#    F10 = 55
+#    F11 = 89
+#    F12 = 144
+#
+#The 12th term, F12, is the first term to contain three digits.
+#What is the index of the first term in the Fibonacci sequence to contain 1000 digits?
+
+def solution(num_digits = 1000)
+  #Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1.
+  resultn1 = 1
+  resultn2 = 1
+  result = 2
+  index = 3
+  value = true
+  while value
+    resultn2 = resultn1
+    resultn1 = result
+    if (resultn1 + resultn2).abs.digits.length < num_digits
+      value = true
+    else
+      value = false
+    end
+    result = resultn1 + resultn2    
+    index += 1
+  end
+  res = index
+end
+
+answer = solution()
+p answer
+