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solution_1.js
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52 lines (48 loc) · 1.6 KB
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"use strict"
function checkPrime(input, list) {
for (let i = 0; i < list.length && list[i] < input ** 0.5; i++)
if (!(input % list[i])) return 0;
return 1;
}
function getNumOfDivisor(input) {
let prime_list = [2,3];
let numDivisors = 1, counter = 1, k = 1;
if (!(input % 2)) {
input /= 2;
while(!(input%2)) ++counter && (input /= 2);
numDivisors *= ++counter;
}
if (!(input % 3)) {
(counter = 1) && (input /= 3);
while(!(input % 3)) ++counter && (input /= 3);
numDivisors *= ++counter;
}
while (6 * k - 1 <= input) {
if (checkPrime(6 * k - 1, prime_list)) {
prime_list.push(6 * k - 1);
if (!(input % (6 * k - 1))) {
(counter = 1) && (input /= (6 * k -1));
while (!(input % (6 * k - 1))) ++counter && (input /= (6 * k -1));
numDivisors *= ++counter;
}
}
if ((6 * k + 1) <= input && checkPrime(6 * k + 1, prime_list)) {
prime_list.push(6 * k + 1);
if (!(input % (6 * k + 1))) {
(counter = 1) && (input /= (6 * k + 1));
while (!(input % (6 * k + 1))) ++counter && (input /= (6 * k + 1));
numDivisors *= ++counter;
}
}
k++;
}
return numDivisors;
}
function getTriangleNumber() {
let n = 45, numDivisors = 0;
while (numDivisors <= 500) {
(numDivisors = getNumOfDivisor(n * (n + 1)/2)) && ++n;
}
return ((n-1) * n / 2);
}
console.log(getTriangleNumber());