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Project Euler problem 014 solution #493

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pomkarnath98 merged 4 commits into from
Feb 13, 2021
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Project Euler problem 014 solution #493

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74d5715
add a solution for Project Euler problem #005
Waddah-JD Oct 15, 2020
03d3720
add a solution for Project Euler problem #006
Waddah-JD Oct 15, 2020
b26baef
remove files to merge from seprate brnches
Waddah-JD Oct 17, 2020
bfcf986
add solution for Project Euler 014
Waddah-JD Oct 17, 2020
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47 changes: 47 additions & 0 deletions Project-Euler/Problem014.js
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/*
Longest Collatz sequence

The following iterative sequence is defined for the set of positive integers:

n → n/2 (n is even)
n → 3n + 1 (n is odd)

Using the rule above and starting with 13, we generate the following sequence:

13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1
It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1.

Which starting number, under one million, produces the longest chain?

NOTE: Once the chain starts the terms are allowed to go above one million.
*/

const getCollatzSequenceLength = (num, seqLength) => {
if (num === 1) {
return seqLength
} else {
let newElement
if (num % 2 === 0) {
newElement = num / 2
} else {
newElement = (3 * num) + 1
}
seqLength++
return getCollatzSequenceLength(newElement, seqLength)
}
}

const findLongestCollatzSequence = () => {
let startingPointForLargestSequence = 1
let largestSequnceLength = 1
for (let i = 2; i < 1000000; i++) {
const currentSequenceLength = getCollatzSequenceLength(i, 1)
if (currentSequenceLength > largestSequnceLength) {
startingPointForLargestSequence = i
largestSequnceLength = currentSequenceLength
}
}
return startingPointForLargestSequence
}

console.log(findLongestCollatzSequence())