September 2017 Update

Task/Ludic-numbers/JavaScript/ludic-numbers.js

@@ -0,0 +1,65 @@
+/**
+ * Boilerplate to simply get an array filled between 2 numbers
+ * @param {!number} s Start here (inclusive)
+ * @param {!number} e End here (inclusive)
+ */
+const makeArr = (s, e) => new Array(e + 1 - s).fill(s).map((e, i) => e + i);
+
+/**
+ * Remove every n-th element from the given array
+ * @param {!Array} arr
+ * @param {!number} n
+ * @return {!Array}
+ */
+const filterAtInc = (arr, n) => arr.filter((e, i) => (i + 1) % n);
+
+/**
+ * Generate ludic numbers
+ * @param {!Array} arr
+ * @param {!Array} result
+ * @return {!Array}
+ */
+const makeLudic = (arr, result) => {
+  const iter = arr.shift();
+  result.push(iter);
+  return arr.length ? makeLudic(filterAtInc(arr, iter), result) : result;
+};
+
+/**
+ * Our Ludic numbers. This is a bit of a cheat, as we already know beforehand
+ * up to where our seed array needs to go in order to exactly get to the
+ * 2005th Ludic number.
+ * @type {!Array<!number>}
+ */
+const ludicResult = makeLudic(makeArr(2, 21512), [1]);
+
+
+// Below is just logging out the results.
+/**
+ * Given a number, return a function that takes an array, and return the
+ * count of all elements smaller than the given
+ * @param {!number} n
+ * @return {!Function}
+ */
+const smallerThanN = n => arr => {
+  return arr.reduce((p,c) => {
+    return c <= n ? p + 1 : p
+  }, 0)
+};
+const smallerThan1K = smallerThanN(1000);
+
+console.log('\nFirst 25 Ludic Numbers:');
+console.log(ludicResult.filter((e, i) => i < 25).join(', '));
+
+console.log('\nTotal Ludic numbers smaller than 1000:');
+console.log(smallerThan1K(ludicResult));
+
+console.log('\nThe 2000th to 2005th ludic numbers:');
+console.log(ludicResult.filter((e, i) => i > 1998).join(', '));
+
+console.log('\nTriplets smaller than 250:');
+ludicResult.forEach(e => {
+  if (e + 6 < 250 && ludicResult.indexOf(e + 2) > 0 && ludicResult.indexOf(e + 6) > 0) {
+    console.log([e, e + 2, e + 6].join(', '));
+  }
+});