2016 Update

Task/Combinations/JavaScript/combinations-6.js

@@ -0,0 +1,47 @@
+(function (n) {
+    'use strict';
+
+
+    // n -> [a] -> [[a]]
+    let comb = (n, xs) => {
+            if (n < 1) return [[]];
+            if (xs.length === 0) return [];
+
+            let h = xs[0],
+                tail = xs.slice(1);
+
+            return comb(n - 1, tail)
+                .map((t) => [h].concat(t))
+                .concat(comb(n, tail));
+        },
+
+
+
+        // Derive a memoized version of a function
+        // Function -> Function
+        memoized = (f) => {
+            let m = {};
+
+            return function (x) {
+                let args = [].slice.call(arguments),
+                    strKey = args.join('-'),
+                    v = m[strKey];
+
+                return (
+                    (v === undefined) &&
+                    (m[strKey] = v = f.apply(null, args)),
+                    v
+                );
+            }
+        },
+
+        range = (m, n) =>
+            Array.from({
+                length: (n - m) + 1
+            }, (_, i) => m + i);
+
+
+    return memoized(comb)(n, range(0, 4))
+
+
+})(3);