Add "Playing with digits" kata

Author: juanantonioledesma

6-kyu/playing-with-digits.md

@@ -0,0 +1,53 @@
+<h1>Playing with digits <sup><sup>6 Kyu</sup></sup></h1>
+
+<sup>
+  <a href="https://www.codewars.com/kata/5552101f47fc5178b1000050">
+    <strong>LINK TO THE KATA</strong>
+  </a> - <code>FUNDAMENTALS</code> <code>MATHEMATICS</code>
+</sup>
+
+## Description
+
+Some numbers have funny properties. For example:
+
+> 89 --> 8¹ + 9² = 89 \* 1
+
+> 695 --> 6² + 9³ + 5⁴= 1390 = 695 \* 2
+
+> 46288 --> 4³ + 6⁴+ 2⁵ + 8⁶ + 8⁷ = 2360688 = 46288 \* 51
+
+Given a positive integer n written as abcd... (a, b, c, d... being digits) and a positive integer p
+
+- we want to find a positive integer k, if it exists, such that the sum of the digits of n taken to the successive powers of p is equal to k \* n.
+
+In other words:
+
+> Is there an integer k such as : (a ^ p + b ^ (p+1) + c ^(p+2) + d ^ (p+3) + ...) = n \* k
+
+If it is the case we will return k, if not return -1.
+
+**Note:** n and p will always be given as strictly positive integers.
+
+```javascript
+digPow(89, 1) should return 1 since 8¹ + 9² = 89 = 89 * 1
+digPow(92, 1) should return -1 since there is no k such as 9¹ + 2² equals 92 * k
+digPow(695, 2) should return 2 since 6² + 9³ + 5⁴= 1390 = 695 * 2
+digPow(46288, 3) should return 51 since 4³ + 6⁴+ 2⁵ + 8⁶ + 8⁷ = 2360688 = 46288 * 51
+```
+
+## Solution
+
+```javascript
+const digPow = (n, p) => {
+  const numbers = n
+    .toString()
+    .split('')
+    .map(character => Number(character))
+
+  const powSum = numbers.reduce((acc, cur, i) => acc + Math.pow(cur, p + i), 0)
+
+  if (powSum === n * p) return p
+  if (powSum % n === 0) return powSum / n
+  return -1
+}
+```

README.md

@@ -53,6 +53,7 @@ JavaScript katas on Codewars are programming challenges that help you improve yo
 - **[Persistent Bugger](./6-kyu/persistent-bugger.md)**
 - **[Piano Kata, Part 1](./6-kyu/piano-kata-part-1.md)**
 - **[Piano Kata, Part 2](./6-kyu/piano-kata-part-2.md)**
+- **[Playing with digits](./6-kyu/playing-with-digits.md)**
 - **[Selective Array Reversing](./6-kyu/selective-array-reversing.md)**
 - **[Simple Fun #212: Processing Requests!](./6-kyu/simple-fun-212-processing-requests.md)**
 - **[Sort the odd](./6-kyu/sort-the-odd.md)**