Add "Josephus Survivor" kata

Author: juan-antonio-ledesma

5-kyu/josephus-survivor.md

@@ -0,0 +1,53 @@
+<h1>Josephus Survivor <sup><sup>5 Kyu</sup></sup></h1>
+
+<sup>
+  <a href="https://www.codewars.com/kata/555624b601231dc7a400017a">
+    <strong>LINK TO THE KATA</strong>
+  </a> - <code>MATHEMATICS</code> <code>COMBINATORICS</code> <code>ALGORITHMS</code> <code>LISTS</code> <code>ARRAYS</code>
+</sup>
+
+## Description
+
+In this kata you have to correctly return who is the "survivor", ie: the last element of a [Josephus permutation](https://www.codewars.com/kata/josephus-permutation/).
+
+Basically you have to assume that n people are put into a circle and that they are eliminated in steps of k elements, like this:
+
+```
+n=7, k=3 => means 7 people in a circle
+one every 3 is eliminated until one remains
+[1,2,3,4,5,6,7] - initial sequence
+[1,2,4,5,6,7] => 3 is counted out
+[1,2,4,5,7] => 6 is counted out
+[1,4,5,7] => 2 is counted out
+[1,4,5] => 7 is counted out
+[1,4] => 5 is counted out
+[4] => 1 counted out, 4 is the last element - the survivor!
+```
+
+The above link about the "base" kata description will give you a more thorough insight about the origin of this kind of permutation, but basically that's all that there is to know to solve this kata.
+
+**Notes and tips:** using the solution to the other kata to check your function may be helpful, but as much larger numbers will be used, using an array/list to compute the number of the survivor may be too slow; you may assume that both n and k will always be >=1.
+
+## Solution
+
+```javascript
+const getCircleOfPersons = num => {
+  const circle = []
+  for (let i = 1; i <= num; i++) {
+    circle.push(i)
+  }
+  return circle
+}
+
+const josephusSurvivor = (n, k) => {
+  const circleOfPersons = getCircleOfPersons(n)
+  let index = 0
+
+  while (circleOfPersons.length > 1) {
+    index = (index + k - 1) % circleOfPersons.length
+    circleOfPersons.splice(index, 1)
+  }
+
+  return circleOfPersons[0]
+}
+```

README.md

@@ -39,6 +39,7 @@ JavaScript katas on Codewars are programming challenges that help you improve yo
 - **[First non-repeating character](./5-kyu/first-non-repeating-character.md)**<br><sup>`STRINGS` `ALGORITHMS`</sup>
 - **[Greed is Good](./5-kyu/greed-is-good.md)**<br><sup>`ALGORITHMS`</sup>
 - **[Human Readable Time](./5-kyu/human-readable-time.md)**<br><sup>`DATE TIME` `MATHEMATICS` `ALGORITHMS`</sup>
+- **[Josephus Survivor](./5-kyu/josephus-survivor.md)**<br><sup>`MATHEMATICS` `COMBINATORICS` `ALGORITHMS` `LISTS` `ARRAYS`</sup>
 - **[Mean Square Error](./5-kyu/mean-square-error.md)**<br><sup>`ARRAYS` `MATHEMATICS` `ALGORITHMS`</sup>
 - **[Moving Zeros To The End](./5-kyu/moving-zeros-to-the-end.md)**<br><sup>`ARRAYS` `SORTING` `ALGORITHMS`</sup>
 - **[Not very secure](./5-kyu/not-very-secure.md)**<br><sup>`REGULAR EXPRESSIONS` `STRINGS`</sup>