3.1 KiB
3.1 KiB
id | challengeType | title |
---|---|---|
5900f3781000cf542c50fe8b | 5 | Problem 12: Highly divisible triangular number |
Description
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
Let us list the factors of the first seven triangle numbers:
1: 1
3: 1, 3
6: 1, 2, 3, 6
10: 1, 2, 5, 10
15: 1, 3, 5, 15
21: 1, 3, 7, 21
28: 1, 2, 4, 7, 14, 28
We can see that 28 is the first triangle number to have over five divisors.
What is the value of the first triangle number to have over n
divisors?
Instructions
Tests
tests:
- text: <code>divisibleTriangleNumber(5)</code> should return 28.
testString: assert.strictEqual(divisibleTriangleNumber(5), 28, '<code>divisibleTriangleNumber(5)</code> should return 28.');
- text: <code>divisibleTriangleNumber(23)</code> should return 630.
testString: assert.strictEqual(divisibleTriangleNumber(23), 630, '<code>divisibleTriangleNumber(23)</code> should return 630.');
- text: <code>divisibleTriangleNumber(167)</code> should return 1385280.
testString: assert.strictEqual(divisibleTriangleNumber(167), 1385280, '<code>divisibleTriangleNumber(167)</code> should return 1385280.');
- text: <code>divisibleTriangleNumber(374)</code> should return 17907120.
testString: assert.strictEqual(divisibleTriangleNumber(374), 17907120, '<code>divisibleTriangleNumber(374)</code> should return 17907120.');
- text: <code>divisibleTriangleNumber(500)</code> should return 76576500.
testString: assert.strictEqual(divisibleTriangleNumber(500), 76576500, '<code>divisibleTriangleNumber(500)</code> should return 76576500.');
Challenge Seed
function divisibleTriangleNumber(n) {
// Good luck!
return true;
}
divisibleTriangleNumber(500);
Solution
function divisibleTriangleNumber(n) {
let counter = 1;
let triangleNumber = counter++;
function getFactors(num) {
let factors = [];
let possibleFactor = 1;
let sqrt = Math.sqrt(num);
while (possibleFactor <= sqrt) {
if (num % possibleFactor == 0) {
factors.push(possibleFactor);
var otherPossibleFactor = num / possibleFactor;
if (otherPossibleFactor > possibleFactor) {
factors.push(otherPossibleFactor);
}
}
possibleFactor++;
}
return factors;
}
while (getFactors(triangleNumber).length < n) {
triangleNumber += counter++;
}
console.log(triangleNumber)
return triangleNumber;
}