feat: kata/neutralisation (#840)

* docs: kata description

* feat: kata/neutralisation

---------

Co-authored-by: ParanoidUser <[email protected]>

Author: github-actions[bot]

kata/8-kyu/index.md

@@ -146,6 +146,7 @@
 - [Multiply](multiply "50654ddff44f800200000004")
 - [My head is at the wrong end!](my-head-is-at-the-wrong-end "56f699cd9400f5b7d8000b55")
 - [Name on billboard](name-on-billboard "570e8ec4127ad143660001fd")
+- [Neutralisation](neutralisation "65128732b5aff40032a3d8f0")
 - [Never visit a . . . !?](never-visit-a "56c5847f27be2c3db20009c3")
 - [No zeros for heroes](no-zeros-for-heros "570a6a46455d08ff8d001002")
 - [OOP: Object Oriented Piracy ](oop-object-oriented-piracy "54fe05c4762e2e3047000add")
@@ -180,7 +181,7 @@
 - [Rock Paper Scissors!](rock-paper-scissors "5672a98bdbdd995fad00000f")
 - [Sentence Smash](sentence-smash "53dc23c68a0c93699800041d")
 - [Short Long Short](short-long-short "50654ddff44f800200000007")
-- [simple calculator ](simple-calculator "5810085c533d69f4980001cf")
+- [Simple calculator ](simple-calculator "5810085c533d69f4980001cf")
 - [Simple Fun #1: Seats in Theater](simple-fun-number-1-seats-in-theater "588417e576933b0ec9000045")
 - [Simple multiplication](simple-multiplication "583710ccaa6717322c000105")
 - [Simple validation of a username with regex](simple-validation-of-a-username-with-regex "56a3f08aa9a6cc9b75000023")

kata/8-kyu/neutralisation/README.md

@@ -0,0 +1,32 @@
+# [Neutralisation](https://www.codewars.com/kata/neutralisation "https://www.codewars.com/kata/65128732b5aff40032a3d8f0")
+
+Given two strings comprised of `+` and `-`, return a new string which shows how the two strings interact in the following way:
+
+- When positives and positives interact, they *remain positive*.
+- When negatives and negatives interact, they *remain negative*.
+- But when negatives and positives interact, they *become neutral*, and are shown as the number `0`.
+
+### Worked Example
+
+```
+("+-+", "+--") ➞ "+-0"
+# Compare the first characters of each string, then the next in turn.
+# "+" against a "+" returns another "+".
+# "-" against a "-" returns another "-".
+# "+" against a "-" returns "0".
+# Return the string of characters.
+```
+
+### Examples
+
+```
+("--++--", "++--++") ➞ "000000"
+
+("-+-+-+", "-+-+-+") ➞ "-+-+-+"
+
+("-++-", "-+-+") ➞ "-+00"
+```
+
+### Notes
+
+The two strings will be the same length.

kata/8-kyu/neutralisation/main/Solution.java

@@ -0,0 +1,8 @@
+import static java.util.stream.Collectors.joining;
+import static java.util.stream.IntStream.range;
+
+interface Solution {
+  static String neutralise(String s1, String s2) {
+    return range(0, s1.length()).mapToObj(i -> s1.charAt(i) == s2.charAt(i) ? s1.charAt(i) + "" : "0").collect(joining());
+  }
+}

kata/8-kyu/neutralisation/test/SolutionTest.java

@@ -0,0 +1,38 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class SolutionTest {
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      '','',''
+      +,+,+
+      -,-,-
+      +,-,0
+      -,+,0
+      -+,++,0+
+      --,-+,-0
+      +--,+--,+--
+      -++,-+-,-+0
+      +-+,-++,00+
+      -++,+--,000
+      -++-,-+-+,-+00
+      --++,++++,00++
+      ---+,-+++,-00+
+      -----,-----,-----
+      --++--,++--++,000000
+      -+-+-+,-+-+-+,-+-+-+
+      +-----+-,---++-++,0--00-+0
+      --+++-+-,+++++---,00+++-0-
+      +++--+---,++----++-,++0--000-
+      -++-+-++-,+-++++---,00+0+000-
+      ---++-+--,-+++--++-,-00+0-+0-
+      ++-++--++-,-+++-++-++,0+0+0000+0
+      +-----+++-,--+-+-++--,0-0-0-++0-
+      -+--+-+---,-+--+-+-+-,-+--+-+-0-
+      """)
+  void sample(String s1, String s2, String expected) {
+    assertEquals(expected, Solution.neutralise(s1, s2));
+  }
+}