Add binomialCoefficient

snippets/binomialCoefficient.md

@@ -0,0 +1,26 @@
+### 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);
+};
+```
+
+```js
+binomialCoefficient(8, 2); // 28
+```

tag_database

@@ -10,6 +10,7 @@ bifurcateBy:array,function
 bind:function,object
 bindAll:object,function
 bindKey:function,object
+binomialCoefficient:math
 bottomVisible:browser
 btoa:node,string,utility
 byteSize:string

test/binomialCoefficient/binomialCoefficient.js

@@ -0,0 +1,11 @@
+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);
+};
+module.exports = binomialCoefficient;

test/binomialCoefficient/binomialCoefficient.test.js

@@ -0,0 +1,18 @@
+const test = require('tape');
+const binomialCoefficient = require('./binomialCoefficient.js');
+
+test('Testing binomialCoefficient', (t) => {
+  //For more information on all the methods supported by tape
+  //Please go to https://github.com/substack/tape
+  t.true(typeof binomialCoefficient === 'function', 'binomialCoefficient is a Function');
+  t.equal(binomialCoefficient(8, 2), 28, 'Returns the appropriate value');
+  t.equal(binomialCoefficient(0, 0), 1, 'Returns the appropriate value');
+  t.equal(binomialCoefficient(5, 3), 10, 'Returns the appropriate value');
+  t.true(Number.isNaN(binomialCoefficient(NaN, 3)), 'Returns NaN');
+  t.true(Number.isNaN(binomialCoefficient(5, NaN)), 'Returns NaN');
+  //t.deepEqual(binomialCoefficient(args..), 'Expected');
+  //t.equal(binomialCoefficient(args..), 'Expected');
+  //t.false(binomialCoefficient(args..), 'Expected');
+  //t.throws(binomialCoefficient(args..), 'Expected');
+  t.end();
+});

test/testlog

@@ -1,4 +1,4 @@
-Test log for: Wed Feb 14 2018 12:24:07 GMT+0200 (GTB Standard Time)
+Test log for: Wed Feb 14 2018 12:33:42 GMT+0200 (GTB Standard Time)
 
 > 30-seconds-of-code@0.0.1 test G:\My Files\git Repositories\30-seconds-of-code
 > tape test/**/*.test.js | tap-spec
@@ -86,6 +86,15 @@ Test log for: Wed Feb 14 2018 12:24:07 GMT+0200 (GTB Standard Time)
     √ bindKey is a Function
     √ Binds function to an object context
 
+  Testing binomialCoefficient
+
+    √ binomialCoefficient is a Function
+    √ Returns the appropriate value
+    √ Returns the appropriate value
+    √ Returns the appropriate value
+    √ Returns NaN
+    √ Returns NaN
+
   Testing bottomVisible
 
     √ bottomVisible is a Function
@@ -1830,8 +1839,8 @@ Test log for: Wed Feb 14 2018 12:24:07 GMT+0200 (GTB Standard Time)
     √ Works with multiple promises
 
 
-  total:     913
-  passing:   913
+  total:     919
+  passing:   919
   duration:  2.4s