diff --git a/README.md b/README.md index 0f083e4a2..0b99c993a 100644 --- a/README.md +++ b/README.md @@ -260,6 +260,7 @@ average(1, 2, 3); * [`average`](#average) * [`averageBy`](#averageby) +* [`binomialCoefficient`](#binomialcoefficient) * [`clampNumber`](#clampnumber) * [`degreesToRads`](#degreestorads) * [`digitize`](#digitize) @@ -4361,6 +4362,41 @@ averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5
[⬆ Back to top](#table-of-contents) +### binomialCoefficient + +Evaluates the binomial coefficient of two integers `n` and `k`. + +Use `Number.isNaN()` to check if any of the two values is `NaN`. +Check if `k` is less than `0`, greater than or equal to `n`, equal to `1` or `n - 1` and return the appropriate result. +Check if `n - k` is less than `k` and switch their values accordingly. +Loop from `2` through `k` and calculate the binomial coefficient. +Use `Math.round()` to account for rounding errors in the calculation. + +```js +const binomialCoefficient = (n, k) => { + if (Number.isNaN(n) || Number.isNaN(k)) return NaN; + if (k < 0 || k > n) return 0; + if (k === 0 || k === n) return 1; + if (k === 1 || k === n - 1) return n; + if (n - k < k) k = n - k; + let res = n; + for (let j = 2; j <= k; j++) res *= (n - j + 1) / j; + return Math.round(res); +}; +``` + +
+Examples + +```js +binomialCoefficient(8, 2); // 28 +``` + +
+ +
[⬆ Back to top](#table-of-contents) + + ### clampNumber Clamps `num` within the inclusive range specified by the boundary values `a` and `b`. diff --git a/docs/index.html b/docs/index.html index 7aa7f51ad..45e2c52bc 100644 --- a/docs/index.html +++ b/docs/index.html @@ -50,7 +50,7 @@ scrollToTop(); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.

 

Adapter

ary

Creates a function that accepts up to n arguments, ignoring any additional arguments.

Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).

const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.
 
Adapter
ary
Creates a function that accepts up to n arguments, ignoring any additional arguments.
Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).
const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
 
const firstTwoMax = ary(Math.max, 2);
 [[2, 6, 'a'], [8, 4, 6], [10]].map(x => firstTwoMax(...x)); // [6, 8, 10]
 
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
@@ -997,6 +997,17 @@ console.log<
   arr.length;
 
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5
 averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5
+
binomialCoefficient
Evaluates the binomial coefficient of two integers n and k.
Use Number.isNaN() to check if any of the two values is NaN. Check if k is less than 0, greater than or equal to n, equal to 1 or n - 1 and return the appropriate result. Check if n - k is less than k and switch their values accordingly. Loop from 2 through k and calculate the binomial coefficient. Use Math.round() to account for rounding errors in the calculation.
const binomialCoefficient = (n, k) => {
+  if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
+  if (k < 0 || k > n) return 0;
+  if (k === 0 || k === n) return 1;
+  if (k === 1 || k === n - 1) return n;
+  if (n - k < k) k = n - k;
+  let res = n;
+  for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;
+  return Math.round(res);
+};
+
binomialCoefficient(8, 2); // 28
 
clampNumber
Clamps num within the inclusive range specified by the boundary values a and b.
If num falls within the range, return num. Otherwise, return the nearest number in the range.
const clampNumber = (num, a, b) => Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b));
 
clampNumber(2, 3, 5); // 3
 clampNumber(1, -1, -5); // -1