directions.

Problem #4

The Fibonacci sequence is defined by the recurrence relation:

Fn = Fn1 + Fn2, where F1 = 1 and F2 = 1.

Hence the first 12 terms will be:

F1 = 1
F2 = 1
F3 = 2
F4 = 3
F5 = 5
F6 = 8
F7 = 13
F8 = 21
F9 = 34
F10 = 55
F11 = 89
F12 = 144

The 12th term, F12, is the first term to contain three digits.

What is the first term in the Fibonacci sequence to contain 1000 digits?

fib.rb

fib_index = 1
fib_current = 1
fib_previous = 0

while fib_current.to_s.length < 1000
  fib_index += 1
  fib_previous, fib_current = fib_current, fib_current + fib_previous
end

puts "Index: #{fib_index}, Sum: #{fib_current}"