freddie2025's solution to Collatz Conjecture on the JavaScript track

Instructions

Test suite

Solution

Note:

This exercise has changed since this solution was written.

The Collatz Conjecture or 3x+1 problem can be summarized as follows:

Take any positive integer n. If n is even, divide n by 2 to get n / 2. If n is odd, multiply n by 3 and add 1 to get 3n + 1. Repeat the process indefinitely. The conjecture states that no matter which number you start with, you will always reach 1 eventually.

Given a number n, return the number of steps required to reach 1.

Examples

Starting with n = 12, the steps would be as follows:

Resulting in 9 steps. So for input n = 12, the return value would be 9.

Setup

Go through the setup instructions for Javascript to install the necessary dependencies:

https://exercism.io/tracks/javascript/installation

Requirements

Install assignment dependencies:

$ npm install

Making the test suite pass

Execute the tests with:

$ npm test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing xtest to test.

Source

An unsolved problem in mathematics named after mathematician Lothar Collatz https://en.wikipedia.org/wiki/3x_%2B_1_problem

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

collatz-conjecture.spec.js

import { steps } from './collatz-conjecture';

describe('steps()', () => {
  test('zero steps for one', () => {
    expect(steps(1)).toEqual(0);
  });

  xtest('divide if even', () => {
    expect(steps(16)).toEqual(4);
  });

  xtest('even and odd steps', () => {
    expect(steps(12)).toEqual(9);
  });

  xtest('Large number of even and odd steps', () => {
    expect(steps(1000000)).toEqual(152);
  });

  xtest('zero is an error', () => {
    expect(() => {
      steps(0);
    }).toThrow(new Error('Only positive numbers are allowed'));
  });

  xtest('negative value is an error', () => {
    expect(() => {
      steps(-15);
    }).toThrow(new Error('Only positive numbers are allowed'));
  });
});

//
// This is only a SKELETON file for the 'Collatz Conjecture' exercise. It's been provided as a
// convenience to get you started writing code faster.
//

export const steps = (n) => {
  
  let count = 0;
  
  if (n > 0) {

    while (n != 1) {
    
      if (n % 2 === 0) {
        n = n / 2;
      }
      else {
        n = (n * 3) + 1;
      } 

      count++;
    }

    return count;
  }
  else {
    throw new Error("Only positive numbers are allowed");
  }
};

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freddie2025's solution

to Collatz Conjecture in the JavaScript Track