Problem of the Day
A new programming or logic puzzle every Mon-Fri

Nth Fibonacci

Building off of yesterday's problem, create a program to calculate the nth number in the Fibonacci Sequence.

There is a way to calculate it in faster than linear runtime but it can be quite complex. A linear solution is quite fine for today.

Permalink: http://problemotd.com/problem/nth-fibonacci/

Comments:

  • Anonymous - 10 years, 7 months ago

    Building on the code from yesterday:

    (defn nth-fibonacci [n]
      (nth (repeatedly (new-fibonacci-generator)) n))
    
    (nth-fibonacci 13)  ; => 377
    

    See yesterday's Clojure submission for "new-fibonacci-generator".

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  • Nick Krichevsky - 10 years, 7 months ago

    Python. limit=int(raw_input()) num1=0 num2=1 for i in range(limit): num=num1+num2 num2=num1 num1=num print num

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  • Nick Krichevsky - 10 years, 7 months ago

    Fixed formatting.

    limit=int(raw_input())
    num1=0
    num2=1
    for i in range(limit):
        num=num1+num2
        num2=num1
        num1=num
        print num
    

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  • Erik Jansson - 10 years, 7 months ago

    Here's a memoized version in Haskell:

    memoizedFib :: Int -> Integer
    memoizedFib n = fiblist !! n
    
    fiblist :: [Integer]
    fiblist = [ fib x | x <- [0..] ]
        where 
            fib :: Int -> Integer
            fib 1 = 1
            fib 2 = 1
            fib n = fiblist !! (n - 1) + fiblist !! (n - 2)
    

    Running it for the 10000th number gives: *Main> memoizedFib 10000 33644764876431783266621612005107543310302148460680063906564769974680081442166662368155595513633734025582065332680836159373734790483865268263040892463056431887354544369559827491606602099884183933864652731300088830269235673613135117579297437854413752130520504347701602264758318906527890855154366159582987279682987510631200575428783453215515103870818298969791613127856265033195487140214287532698187962046936097879900350962302291026368131493195275630227837628441540360584402572114334961180023091208287046088923962328835461505776583271252546093591128203925285393434620904245248929403901706233888991085841065183173360437470737908552631764325733993712871937587746897479926305837065742830161637408969178426378624212835258112820516370298089332099905707920064367426202389783111470054074998459250360633560933883831923386783056136435351892133279732908133732642652633989763922723407882928177953580570993691049175470808931841056146322338217465637321248226383092103297701648054726243842374862411453093812206564914032751086643394517512161526545361333111314042436854805106765843493523836959653428071768775328348234345557366719731392746273629108210679280784718035329131176778924659089938635459327894523777674406192240337638674004021330343297496902028328145933418826817683893072003634795623117103101291953169794607632737589253530772552375943788434504067715555779056450443016640119462580972216729758615026968443146952034614932291105970676243268515992834709891284706740862008587135016260312071903172086094081298321581077282076353186624611278245537208532365305775956430072517744315051539600905168603220349163222640885248852433158051534849622434848299380905070483482449327453732624567755879089187190803662058009594743150052402532709746995318770724376825907419939632265984147498193609285223945039707165443156421328157688908058783183404917434556270520223564846495196112460268313970975069382648706613264507665074611512677522748621598642530711298441182622661057163515069260029861704945425047491378115154139941550671256271197133252763631939606902895650288268608362241082050562430701794976171121233066073310059947366875

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  • Erik Jansson - 10 years, 7 months ago

    And yes, I'm basically just showing off Haskell's laziness with that output ;)

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  • Anonymous - 10 years, 6 months ago

    #python 2.7
    def nth_fib(n):
        phi = (1+5**(0.5))/2
        nth = int(round( (phi)**n / (5**(0.5)) ))
        return nth
    

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