freeCodeCamp/curriculum/challenges/espanol/10-coding-interview-prep/rosetta-code/fibonacci-word.md

id	title	challengeType	forumTopicId	dashedName
5992e222d397f00d21122931	Fibonacci word	5	302269	fibonacci-word

--description--

The Fibonacci Word may be created in a manner analogous to the Fibonacci Sequence as described here:

Define  F_Word1  as  1
Define  F_Word2  as  0
Form   F_Word3  as  F_Word2   concatenated with  F_Word1   i.e.:  01
Form   F_Wordn  as  F_Wordn-1  concatenated with  F_wordn-2

--instructions--

Write a function to return the Fibonacci Words up to n. n will be provided as a parameter to the function. The function should return an array of objects. The objects should be of the form: { N: 1, Length: 1, Entropy: 0, Word: '1' }.

--hints--

fibWord should be a function.

assert(typeof fibWord === 'function');

fibWord(5) should return an array.

assert(Array.isArray(fibWord(5)));

fibWord(5) should return [{ N:1, Length:1, Entropy:0, Word:"1" },{ N:2, Length:1, Entropy:0, Word:"0" },{ N:3, Length:2, Entropy:1, Word:"01" },{ N:4, Length:3, Entropy:0.9182958340544896, Word:"010" },{ N:5, Length:5, Entropy:0.9709505944546688, Word:"01001" }].

assert.deepEqual(fibWord(5), ans);

--seed--

--after-user-code--

let ans=[ { N: 1, Length: 1, Entropy: 0, Word: '1' },

  { N: 2, Length: 1, Entropy: 0, Word: '0' },

  { N: 3, Length: 2, Entropy: 1, Word: '01' },

  { N: 4, Length: 3, Entropy: 0.9182958340544896, Word: '010' },

  { N: 5, Length: 5, Entropy: 0.9709505944546688, Word: '01001' }];

--seed-contents--

function fibWord(n) {

}

--solutions--

function fibWord(n) {
    function entropy(s) {
         //create an object containing each individual char
      //and the amount of iterations per char
        function prob(s) {
            var h = Object.create(null);
            s.split('').forEach(function(c) {
               h[c] && h[c]++ || (h[c] = 1);
            });
            return h;
        }

        s = s.toString(); //just in case
        var e = 0, l = s.length, h = prob(s);

        for (var i in h ) {
            var p = h[i]/l;
            e -= p * Math.log(p) / Math.log(2);
        }
        return e;
    }
    var wOne = "1", wTwo = "0", wNth = [wOne, wTwo], w = "", o = [];

    for (var i = 0; i < n; i++) {
        if (i === 0 || i === 1) {
            w = wNth[i];
        } else {
            w = wNth[i - 1] + wNth[i - 2];
            wNth.push(w);
        }
        var l = w.length;
        var e = entropy(w);

        if (l <= 21) {
            o.push({
                N: i + 1,
                Length: l,
                Entropy: e,
                Word: w
            });
        } else {
            o.push({
                N: i + 1,
                Length: l,
                Entropy: e,
                Word: "..."
            });
        }
    }
  return o;
}