Nest all content into snippets

snippets/js/s/binomial-coefficient.md

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+---
+title: Binomial coefficient
+type: snippet
+language: javascript
+tags: [math,algorithm]
+cover: blue-red-mountain
+dateModified: 2020-12-28T13:49:24+02:00
+---
+
+Calculates the number of ways to choose `k` items from `n` items without repetition and without order.
+
+- 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);
+};
+```
+
+```js
+binomialCoefficient(8, 2); // 28
+```