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iterated-digits-squaring.js
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iterated-digits-squaring.js
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// If you add the square of the digits of a Natural number
// (an integer bigger than zero), you always end with either 1 or 89:
// 15 -> 26 -> 40 -> 16 -> 37 -> 58 -> 89
// Write a function that takes a number as a parameter and returns
// 1 or 89 after performing the mentioned process.
// Count how many number chains for integers 1 <= n < 1_000_000
// (1 <= n < 100_000_000) end with a value 89.
function iteratedSquare (n) {
while (true) {
if (n === 1 || n === 89) return n;
n = `${n}`.split('').reduce((acc, item) => acc + Math.pow(parseInt(item), 2), 0);
}
}
console.log(iteratedSquare(70)); // 1
function getNumberOfChains () {
const memo = {};
function iteratedSquare (n) {
let number = n;
while (true) {
if (number === 1 || number === 89) {
memo[n] = number;
return number;
}
if (memo[number]) {
memo[n] = memo[number];
return memo[number];
}
number = `${number}`.split('').reduce((acc, item) => acc + Math.pow(parseInt(item), 2), 0);
}
}
let count = 0;
for (let i = 1; i < 1000000; i++) {
if (iteratedSquare(i) === 89) count++;
}
return count;
}
console.log(getNumberOfChains()); // 856929