Fibonacci for 2016! Hard core version!

Computer Science Level 3

Find the sum of digits of the 201 6 th 2016^\text{th} Fibonacci number .


The answer is 1935.

Milan Milanic by Milan Milanic , 24, Serbia

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2 solutions

Bill Bell
Feb 20, 2016

Python 3. May be compared with the Scheme solution. 

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def Fib():
    t0=1
    t1=1
    yield 1,t0
    yield 2,t1
    n=2
    while True:
        t0,t1=t1,t0+t1
        n+=1
        yield n,t1

for n,f in Fib():
    if n==2016:
        print (sum([int(d) for d in str(f)]))
        break

2 Helpful 0 Interesting 0 Brilliant 0 Confused

same way! +1

Department 8 - 5 years, 3 months ago
Brian Riccardi
Feb 14, 2016

Scheme is very useful with this questions :D 

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(define f
  (lambda (n N n1 n2)
    (if (= n N) n1 (f (+ n 1) N (+ n1 n2) n1)
)))

(define dig-sum
  (lambda (s)
    (if (string=? s "") 0 (+ (- (char->integer (string-ref s 0)) 48) (dig-sum (substring s 1)))
)))

and run 

1
 
(dig-sum (number->string (f 2 2016 1 1)))

1 Helpful 0 Interesting 0 Brilliant 0 Confused

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