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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;
}

1.7 KiB Raw Blame History