- Added guest contribution by Robert DiCicco.

1 files changed, 48 insertions, 0 deletions

diff --git a/challenge-149/robert-dicicco/ruby/ch-1.rb b/challenge-149/robert-dicicco/ruby/ch-1.rb
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+#!ruby.exe
+
+# Author: Robert DiCicco
+# Date: 26-JAN-2022
+# Challenge 149 Fibonacci Digit Sum (Ruby)
+
+def SingleSumOfDigits (num)
+    digsum = num.digits.reverse.sum
+end
+
+def IsPerfectSquare(num)
+    Integer.sqrt(num) ** 2  == num
+end
+
+def IsFibonacci(n)
+    # n is Fibonacci if one of 5*n*n + 4 or 5*n*n - 4 or both
+    # is a perfect square
+
+    if IsPerfectSquare(5*n*n + 4) then
+        return true
+    end
+
+    if IsPerfectSquare(5*n*n - 4) then
+        return true
+    end
+
+    return false
+end
+
+expected = [0, 1, 2, 3, 5, 8, 10, 11, 12, 14, 17, 20, 21, 23, 26, 30, 32, 35, 41, 44]
+
+cnt=0
+total=0
+arr_output = []
+
+# Get first 20 fibonacci numbers
+while total < 20 do
+    sumval = SingleSumOfDigits(cnt)  # get digits sum, then check if fibonacci
+    if(IsFibonacci(sumval)) then
+        arr_output.push(cnt)
+        total += 1  # keep track of how many are output
+    end
+
+    cnt += 1    # bump cnt
+end
+
+puts "Expected: " + expected.to_s + " "
+puts "Output:   " + arr_output.to_s + " "