freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-74-digit-factorial-chains.english.md

id, challengeType, title, forumTopicId

id	challengeType	title	forumTopicId
5900f3b61000cf542c50fec9	5	Problem 74: Digit factorial chains	302187

Description

The number 145 is well known for the property that the sum of the factorial of its digits is equal to 145: 1! + 4! + 5! = 1 + 24 + 120 = 145 Perhaps less well known is 169, in that it produces the longest chain of numbers that link back to 169; it turns out that there are only three such loops that exist: 169 → 363601 → 1454 → 169 871 → 45361 → 871 872 → 45362 → 872 It is not difficult to prove that EVERY starting number will eventually get stuck in a loop. For example, 69 → 363600 → 1454 → 169 → 363601 (→ 1454) 78 → 45360 → 871 → 45361 (→ 871) 540 → 145 (→ 145) Starting with 69 produces a chain of five non-repeating terms, but the longest non-repeating chain with a starting number below one million is sixty terms. How many chains, with a starting number below one million, contain exactly sixty non-repeating terms?

Instructions

Tests

tests:
  - text: <code>euler74()</code> should return 402.
    testString: assert.strictEqual(euler74(), 402);

Challenge Seed

function euler74() {
  // Good luck!
  return true;
}

euler74();

Solution

// solution required