1.7 KiB
1.7 KiB
title | id | challengeType |
---|---|---|
Evaluate binomial coefficients | 598de241872ef8353c58a7a2 | 5 |
Description
Write a function to calculate the binomial coefficient for the given value of n and k.
This formula is recommended:
$\binom{n}{k} = \frac{n!}{(n-k)!k!} = \frac{n(n-1)(n-2)\ldots(n-k+1)}{k(k-1)(k-2)\ldots 1}$Instructions
Tests
tests:
- text: <code>binom</code> is a function.
testString: assert(typeof binom === 'function', '<code>binom</code> is a function.');
- text: <code>binom(5,3)</code> should return 10.
testString: assert.equal(binom(5, 3), 10, '<code>binom(5,3)</code> should return 10.');
- text: <code>binom(7,2)</code> should return 21.
testString: assert.equal(binom(7, 2), 21, '<code>binom(7,2)</code> should return 21.');
- text: <code>binom(10,4)</code> should return 210.
testString: assert.equal(binom(10, 4), 210, '<code>binom(10,4)</code> should return 210.');
- text: <code>binom(6,1)</code> should return 6.
testString: assert.equal(binom(6, 1), 6, '<code>binom(6,1)</code> should return 6.');
- text: <code>binom(12,8)</code> should return 495.
testString: assert.equal(binom(12, 8), 495, '<code>binom(12,8)</code> should return 495.');
Challenge Seed
function binom (n, k) {
// Good luck!
}
Solution
function binom(n, k) {
let coeff = 1;
for (let i = n - k + 1; i <= n; i++) coeff *= i;
for (let i = 1; i <= k; i++) coeff /= i;
return coeff;
}