[Hacker Rank] Warm up: Birthday Cake Candles solved ✓

Author: Gonzalo Diaz

algorithm-exercises-java/src/main/java/ae/hackerrank/warmup/BirthdayCakeCandles.java

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+package ae.hackerrank.warmup;
+
+import java.util.List;
+
+/**
+ * Birthday Cake Candles.
+ *
+ * @link Problem definition [[docs/hackerrank/warmup/solve_me_first.md]]
+ */
+public class BirthdayCakeCandles {
+
+  private BirthdayCakeCandles() {
+  }
+
+  static java.util.logging.Logger logger = util.CustomLogger.getLogger();
+
+  /**
+   * birthdayCakeCandles.
+   */
+  public static int birthdayCakeCandles(List<Integer> candles) {
+    if (candles == null || candles.isEmpty()) {
+      throw new IllegalArgumentException("Parameter cannot be empty");
+    }
+
+    int counter = 0;
+    int maximum = candles.get(0);
+
+    for (Integer element : candles) {
+      if (element > maximum) {
+        maximum = element;
+        counter = 1;
+      } else {
+        if (element == maximum) {
+          counter += 1;
+        }
+      }
+    }
+
+    return counter;
+  }
+}

algorithm-exercises-java/src/test/java/ae/hackerrank/warmup/BirthdayCakeCandlesTest.java

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+package ae.hackerrank.warmup;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.TestInstance.Lifecycle;
+
+
+@TestInstance(Lifecycle.PER_CLASS)
+class BirthdayCakeCandlesTest {
+  public class BirthdayCakeCandlesTestCase {
+    public List<Integer> candles;
+    public Integer expected;
+
+    public BirthdayCakeCandlesTestCase(List<Integer> _candles, Integer _expected) {
+      this.candles = _candles;
+      this.expected = _expected;
+    }
+  }
+
+  public List<BirthdayCakeCandlesTestCase> testCases;
+
+  @BeforeAll
+  public void setup() {
+    this.testCases = Arrays.asList(
+      new BirthdayCakeCandlesTestCase(
+        Arrays.asList(3, 2, 1, 3),
+        2
+      ),
+      new BirthdayCakeCandlesTestCase(
+        Arrays.asList(1, 2, 3, 3),
+        2
+      )
+    );
+  }
+
+  @Test void birthdayCakeCandles() {
+    for (BirthdayCakeCandlesTestCase testCase : this.testCases) {
+      Integer solutionFound = BirthdayCakeCandles.birthdayCakeCandles(testCase.candles);
+
+      assertEquals(testCase.expected, solutionFound,
+          String.format("%s(%s) answer must be: %d",
+            "CompareTriplets.compareTriplets",
+            testCase.candles.toString(),
+            testCase.expected)
+      );
+    }
+  }
+
+  @Test
+  void testMiniMaxSumNullInput() {
+
+    IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
+      BirthdayCakeCandles.birthdayCakeCandles(null);
+    });
+
+    String expectedMessage = "Parameter cannot be empty";
+    String actualMessage = exception.getMessage();
+
+    assertTrue(actualMessage.contains(expectedMessage));
+  }
+
+  @Test
+  void testMiniMaxSumEmptyInput() {
+    List<Integer> input = Arrays.asList();
+
+    IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
+      BirthdayCakeCandles.birthdayCakeCandles(input);
+    });
+
+    String expectedMessage = "Parameter cannot be empty";
+    String actualMessage = exception.getMessage();
+
+    assertTrue(actualMessage.contains(expectedMessage));
+  }
+}

docs/hackerrank/warmup/birthday_cake_candles.md

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+# [Birthday Cake Candles](https://www.hackerrank.com/challenges/birthday-cake-candles)
+
+Difficulty: #easy
+Category: #warmup
+
+You are in charge of the cake for a child's birthday.
+You have decided the cake will have one candle for each year of their total
+age. They will only be able to blow out the tallest of the candles.
+Count how many candles are tallest.
+
+## Example
+
+The maximum height candles are 4 units high.
+There are 2 of them, so return 2.
+
+## Function Description
+
+Complete the function birthdayCakeCandles in the editor below.
+birthdayCakeCandles has the following parameter(s):
+
+- int candles[n]: the candle heights
+
+## Returns
+
+- int: the number of candles that are tallest
+
+## Input Format
+
+The first line contains a single integer, n, the size of candles[].
+The second line contains  space-separated integers, where each integer i describes
+the height of candles[i].
+
+## Constraints
+
+$ 1 \leq n \leq 10^5 $
+$ 1 \leq candles[i] \leq 10^7 $
+
+## Sample Input 0
+
+```text
+4
+3 2 1 3
+```
+
+## Sample Output 0
+
+```text
+2
+```
+
+## Explanation 0
+
+Candle heights are $ [3, 2, 1, 3] $. The tallest candles are $ 3 $ units, and there
+are $ 2 $ of them.