Problem 49

function isPrime(number) {

if (number == 1) {return false}

const threshold = Math.ceil(Math.sqrt(number))

for (let i = 2; i < threshold+ 1; i++) {

if ( number % i === 0) {

return false;

}

}

return true;

}

function numberToArray(inputNumber) {

return inputNumber.toString().split('').map(x => parseInt(x));

}

function arrayToNumber(inputArr) {

return [...inputArr].reverse().reduce((a,b,index) => a + b * 10 ** index, 0)

}

function findAllPrimePermutations(inputNumber) {

const inputArr = numberToArray(inputNumber);

const findNext = (chosenArr, toChooseArr) => {

if (toChooseArr.length === 0) { return [chosenArr]}

numArr = []

for (let i = 0; i < toChooseArr.length; i++) {

const b = [...toChooseArr];

const c = b.splice(i,1);

numArr = [...numArr, ...findNext([...chosenArr, ...c], [...b])]

}

return numArr;

}

return findNext([], [...inputArr]).map(arrayToNumber).filter(isPrime).filter(removeIfDuplicate)

}

function removeIfDuplicate(element, index, array) {

for (let i = 0; i < index; i++) {

if (array[i] === element) { return false; }

}

return true;

}

// console.log(findAllPrimePermutations(1009))

function collectDistances(inputArr) {

const workArr = [...inputArr]

workArr.sort();

const resultArr = [];

for (let i = 0; i < workArr.length; i++) {

for (let j = i + 1; j < workArr.length; j++) {

resultArr.push([workArr[i], workArr[j], workArr[j] - workArr[i]]);

}

}

return resultArr;

}

// console.log(collectDistances(findAllPrimePermutations(1487)).sort())

function findSolution() {

const resultArr = []

for (let i = 1000; i < 10000; i++) {

if (!isPrime(i)) {continue}

const workArr = collectDistances(findAllPrimePermutations(i)).sort((a,b) => (b[2]-a[2]))

for (let j =1; j < workArr.length; j++) {

if (workArr[j][2] === workArr[j-1][2] && ((workArr[j-1][1] == workArr[j][0]) ||(workArr[j-1][1] == workArr[j][0]))) {

resultArr.push([workArr[j-1][0], workArr[j-1][1], workArr[j][1]])

}

}

}

return resultArr

}

console.log(findSolution())