feat: kata/simple-sum-of-pairs

docs/README.md

@@ -25,7 +25,7 @@ slug.
 
 | [1 kyu](/kata/1-kyu/index.md) | [2 kyu](/kata/2-kyu/index.md) | [3 kyu](/kata/3-kyu/index.md) | [4 kyu](/kata/4-kyu/index.md) | [5 kyu](/kata/5-kyu/index.md) | [6 kyu](/kata/6-kyu/index.md) | [7 kyu](/kata/7-kyu/index.md) | [8 kyu](/kata/8-kyu/index.md) | [beta](/kata/beta/index.md) | [retired](/kata/retired/index.md) |
 |:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:---------------------------:|:---------------------------------:|
-| 0 | 1 | 2 | 26 | 48 | 441 | 605 | 227 | 56 | 82 |
+| 0 | 1 | 2 | 26 | 48 | 442 | 605 | 227 | 56 | 82 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/6-kyu/index.md

@@ -352,6 +352,7 @@
 - [Simple ROT13.5 cypher](simple-rot13-dot-5-cypher)
 - [Simple square numbers](simple-square-numbers)
 - [Simple string indices](simple-string-indices)
+- [Simple sum of pairs](simple-sum-of-pairs)
 - [Simple time difference](simple-time-difference)
 - [Simpson's Rule - Approximate Integration](simpsons-rule-approximate-integration)
 - [Single character palindromes](single-character-palindromes)

kata/6-kyu/simple-sum-of-pairs/README.md

@@ -0,0 +1,20 @@
+# [Simple sum of pairs](https://www.codewars.com/kata/simple-sum-of-pairs "https://www.codewars.com/kata/5bc027fccd4ec86c840000b7")
+
+Given an integer `n`, find two integers `a` and `b` such that:
+
+```
+A) a >= 0 and b >= 0
+B) a + b = n
+C) DigitSum(a) + Digitsum(b) is maximum of all possibilities. 
+```
+
+You will return the digitSum(a) + digitsum(b).
+
+```
+For example:
+solve(29) = 11. If we take 15 + 14 = 29 and digitSum = 1 + 5 + 1 + 4 = 11. There is no larger outcome.
+```
+
+`n` will not exceed `10e10`.
+
+More examples in test cases.

kata/6-kyu/simple-sum-of-pairs/main/Solution.java

@@ -0,0 +1,9 @@
+import java.util.function.LongToIntFunction;
+
+interface Solution {
+  static int solve(long n) {
+    LongToIntFunction sum = l -> (l + "").chars().map(c -> c - 48).sum();
+    long a = (long) Math.pow(10, Math.floor(Math.log10(n))) - 1;
+    return (int) (n > 1 ? sum.applyAsInt(a) + sum.applyAsInt(n - a) : n);
+  }
+}

kata/6-kyu/simple-sum-of-pairs/test/SolutionTest.java

@@ -0,0 +1,21 @@
+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
+      1, 1
+      18, 18
+      29, 11
+      1140, 33
+      50000000, 68
+      458453062, 109
+      8130375074, 119
+      """)
+  void sample(long n, int sum) {
+    assertEquals(sum, Solution.solve(n));
+  }
+}