feat: kata/number-to-digit-tiers (#642)

docs/README.md

@@ -1,7 +1,7 @@
 # Codewars Handbook ☕️🚀
 
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@@ -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 | 430 | 577 | 214 | 56 | 79 |
+| 0 | 1 | 2 | 26 | 48 | 430 | 578 | 214 | 56 | 79 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/7-kyu/index.md

@@ -353,6 +353,7 @@
 - [Number of People in the Bus](number-of-people-in-the-bus)
 - [Number of Rectangles in a Grid](number-of-rectangles-in-a-grid)
 - [Number-Star ladder](number-star-ladder)
+- [Number to digit tiers](number-to-digit-tiers)
 - [Numbers in strings](numbers-in-strings)
 - [Numbers Which Sum of Powers of Its Digits Is The Same Number](numbers-which-sum-of-powers-of-its-digits-is-the-same-number)
 - [Numbers with d occurrences of digit d](numbers-with-d-occurences-of-digit-d)

kata/7-kyu/number-to-digit-tiers/README.md

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+# [Number to digit tiers](https://www.codewars.com/kata/number-to-digit-tiers "https://www.codewars.com/kata/586bca7fa44cfc833e00005c")
+
+Create a function that takes a number and returns an array of strings containing the number cut off at each digit.
+
+### Examples
+
+* `420` should return `["4", "42", "420"]`
+* `2017` should return `["2", "20", "201", "2017"]`
+* `2010` should return `["2", "20", "201", "2010"]`
+* `4020` should return `["4", "40", "402", "4020"]`
+* `80200` should return `["8", "80", "802", "8020", "80200"]`
+
+PS: The input is guaranteed to be an integer in the range `[0, 1000000]`

kata/7-kyu/number-to-digit-tiers/main/Solution.java

@@ -0,0 +1,8 @@
+import static java.util.stream.IntStream.range;
+
+interface Solution {
+  static String[] createArrayOfTiers(int num) {
+    var s = num + "";
+    return range(0, s.length()).mapToObj(i -> s.substring(0, i + 1)).toArray(String[]::new);
+  }
+}

kata/7-kyu/number-to-digit-tiers/test/SolutionTest.java

@@ -0,0 +1,26 @@
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class SolutionTest {
+  private static Stream<Arguments> testData() {
+    return Stream.of(
+        Arguments.of(0, new String[]{"0"}),
+        Arguments.of(6, new String[]{"6"}),
+        Arguments.of(420, new String[]{"4", "42", "420"}),
+        Arguments.of(2017, new String[]{"2", "20", "201", "2017"}),
+        Arguments.of(2010, new String[]{"2", "20", "201", "2010"}),
+        Arguments.of(4020, new String[]{"4", "40", "402", "4020"}),
+        Arguments.of(80200, new String[]{"8", "80", "802", "8020", "80200"})
+    );
+  }
+
+  @ParameterizedTest
+  @MethodSource("testData")
+  void sample(int num, String[] expected) {
+    assertArrayEquals(expected, Solution.createArrayOfTiers(num));
+  }
+}