feat: kata/sum-the-strings (#802)

* docs: kata description

* feat: kata/sum-the-strings

---------

Co-authored-by: ParanoidUser <5120290+ParanoidUser@users.noreply.github.com>

Author: github-actions[bot]

kata/8-kyu/index.md

@@ -196,6 +196,7 @@
 - [Sum of differences in array](sum-of-differences-in-array "5b73fe9fb3d9776fbf00009e")
 - [Sum of Multiples](sum-of-multiples "57241e0f440cd279b5000829")
 - [Sum of positive](sum-of-positive "5715eaedb436cf5606000381")
+- [Sum The Strings](sum-the-strings "5966e33c4e686b508700002d")
 - [Sum without highest and lowest number](sum-without-highest-and-lowest-number "576b93db1129fcf2200001e6")
 - [Surface  Area and Volume of a Box](surface-area-and-volume-of-a-box "565f5825379664a26b00007c")
 - [Swap Values](swap-values "5388f0e00b24c5635e000fc6")

kata/8-kyu/sum-the-strings/README.md

@@ -0,0 +1,19 @@
+# [Sum The Strings](https://www.codewars.com/kata/sum-the-strings "https://www.codewars.com/kata/5966e33c4e686b508700002d")
+
+Create a function that takes 2 integers in form of a string as an input, and outputs the sum (also as a string):
+
+Example: (**Input1, Input2 -->Output**)
+
+```
+"4", "5" --> "9"
+"34", "5" --> "39"
+"", "" --> "0"
+"2", "" --> "2"
+"-5", "3" --> "-2"
+```
+
+Notes:
+
+- If either input is an empty string, consider it as zero.
+
+- Inputs and the expected output will never exceed the signed 32-bit integer limit (`2^31 - 1`)

kata/8-kyu/sum-the-strings/main/Kata.java

@@ -0,0 +1,5 @@
+interface Kata {
+  static String sumStr(String a, String b) {
+    return (a.isEmpty() ? 0 : Integer.parseInt(a)) + (b.isEmpty() ? 0 : Integer.parseInt(b)) + "";
+  }
+}

kata/8-kyu/sum-the-strings/test/SolutionTest.java

@@ -0,0 +1,18 @@
+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 = """
+      4, 5, 9
+      34, 5, 39
+      '', 8, 8
+      9, '', 9
+      '', '', 0
+      """)
+  void sample(String a, String b, String expected) {
+    assertEquals(expected, Kata.sumStr(a, b));
+  }
+}