hackerrank: Resolved failing test cases and added a check for mixed input skills

Author: shortthirdman

src/main/java/com/shortthirdman/quickstart/hackerrank/TeamEfficiencyCalculator.java

@@ -6,12 +6,19 @@
 public class TeamEfficiencyCalculator {
 
     public long getTotalEfficiency(List<Integer> skill) {
-        if (skill == null || skill.size() % 2 != 0) {
+        if (skill == null || skill.isEmpty() || skill.size() % 2 != 0) {
             return -1; // Can't form teams if the list is null or the number of participants isn't even
         }
 
         Collections.sort(skill); // Sort the skills to easily form pairs
         int n = skill.size();
+
+        // Additional check for mixed positive and negative skills
+        // This ensures that if there are both negative and positive values, pairing is invalid.
+        if (skill.getFirst() < 0 && skill.get(n - 1) > 0) {
+            return -1;
+        }
+
         long totalEfficiency = 0;
         int targetSum = skill.getFirst() + skill.get(n - 1); // Calculate the target sum of skills for all pairs
 

src/test/java/com/shortthirdman/quickstart/hackerrank/TeamEfficiencyCalculatorTest.java

@@ -26,7 +26,7 @@ void tearDown() {
     public void testValidInput() {
         // Test with a valid input where pairs satisfy the condition
         List<Integer> skill = Arrays.asList(1, 2, 3, 4);
-        long expected = 14; // (1 * 4) + (2 * 3) = 14
+        long expected = 10; // (1 * 4) + (2 * 3) = 10
         assertEquals(expected, app.getTotalEfficiency(skill));
     }
 
@@ -52,7 +52,7 @@ public void testEmptyInput() {
     @Test
     public void testInvalidPairing() {
         // Test where pairs cannot form the same sum
-        List<Integer> skill = Arrays.asList(1, 2, 5, 6);
+        List<Integer> skill = Arrays.asList(1, 2, 3, 6);
         assertEquals(-1, app.getTotalEfficiency(skill));
     }
 
@@ -68,7 +68,7 @@ public void testAllZeroes() {
     public void testNegativeSkills() {
         // Test with negative skill values
         List<Integer> skill = Arrays.asList(-1, -2, -3, -4);
-        long expected = 14; // (-4 * -1) + (-3 * -2) = 14
+        long expected = 10; // (-4 * -1) + (-3 * -2) = 10
         assertEquals(expected, app.getTotalEfficiency(skill));
     }
 
@@ -84,6 +84,7 @@ public void testLargeInput() {
         // Test with a large input size
         List<Integer> skill = Arrays.asList(10, 20, 30, 40, 50, 60, 70, 80);
         long expected = 2200; // For sorted list, pairing and summing the products satisfies
-        assertEquals(expected, app.getTotalEfficiency(skill));
+        assertNotEquals(expected, app.getTotalEfficiency(skill));
+        assertEquals(6000, app.getTotalEfficiency(skill));
     }
 }