Solving fabonacci problem from http://code-warrior.herokuapp.com.

readme.md

#Fabonacci

Write a function to return fabonacci sequence for n

Defination

f(n) = f(n - 1) + f(n - 2)

when n = 0, f(n) = 0, n = 1, f(n) = 1

Hint

Watch out when handling large number of n, how can you speed up the excution time?

Extra

Resolve in iteration, with fewest varible.

##Powerd by CodeWarrior

index.js

var cache = {};

var fabonacci = module.exports = function(n) {
  if (n == 0) return 0;
  if (n == 1) return 1;
  if (!cache[n]) {
    cache[n] = fabonacci(n - 1) + fabonacci(n - 2);
  }
  return cache[n];
}

var iterationFab = function(n) {
  if (n == 0) return 0;
  if (n == 1) return 1;

  var a = 0, b = 1, val = 0;

  for (var i = 1; i < n; i++) {
    val = a + b;
    a = b;
    b = val;
  };
  return val;
}

package.json

{
  "id": 2,
  "name": "fabonacci",
  "level": "basic",
  "author": "Jimmy Chao"
}

test.js

var expect = require('expect.js');

var fab = require('./');

describe("fabonacci", function() {
  it("should handle base case", function() {
    expect(fab(0)).to.equal(0);
    expect(fab(1)).to.equal(1);
    expect(fab(2)).to.equal(1);
  });

  it("should return correct sequence", function() {
    expect(fab(6)).to.equal(8);
    expect(fab(7)).to.equal(13);
    expect(fab(8)).to.equal(21);
    expect(fab(9)).to.equal(34);
    expect(fab(10)).to.equal(55);
  });

  it("should return correct number", function() {
    expect(fab(14)).to.equal(377);
    expect(fab(20)).to.equal(6765);
    expect(fab(36)).to.equal(14930352);
    expect(fab(44)).to.equal(701408733);
  });

  it("should fast enough to run big number", function() {
    expect(fab(1000)).to.eql(4.346655768693743e+208);
  });
});