Fix CombinationSumTest to use static method calls

Removed all instances of 'new CombinationSum()' in testBasicCase, testMultipleCombinations, and testNoSolution methods. Updated all calls to use the static method CombinationSum.combinationSum() directly instead of creating an instance, as the CombinationSum class has a private constructor and is designed to be used statically.

Author: Tejasrahane

src/test/java/com/thealgorithms/recursion/CombinationSumTest.java

@@ -1,52 +1,42 @@
 package com.thealgorithms.recursion;
-
 import static org.junit.jupiter.api.Assertions.*;
-
 import java.util.Arrays;
 import java.util.List;
 import org.junit.jupiter.api.Test;
-
 /**
  * Comprehensive test class for CombinationSum algorithm
  * Tests various scenarios including edge cases
  */
 class CombinationSumTest {
-
     @Test
     void testBasicCase() {
-        CombinationSum cs = new CombinationSum();
         int[] candidates = {2, 3, 6, 7};
         int target = 7;
-        List<List<Integer>> result = cs.combinationSum(candidates, target);
+        List<List<Integer>> result = CombinationSum.combinationSum(candidates, target);
 
         assertTrue(result.contains(Arrays.asList(2, 2, 3)));
         assertTrue(result.contains(Arrays.asList(7)));
         assertEquals(2, result.size());
     }
-
     @Test
     void testMultipleCombinations() {
-        CombinationSum cs = new CombinationSum();
         int[] candidates = {2, 3, 5};
         int target = 8;
-        List<List<Integer>> result = cs.combinationSum(candidates, target);
+        List<List<Integer>> result = CombinationSum.combinationSum(candidates, target);
 
         assertTrue(result.contains(Arrays.asList(2, 2, 2, 2)));
         assertTrue(result.contains(Arrays.asList(2, 3, 3)));
         assertTrue(result.contains(Arrays.asList(3, 5)));
         assertEquals(3, result.size());
     }
-
     @Test
     void testNoSolution() {
-        CombinationSum cs = new CombinationSum();
         int[] candidates = {2};
         int target = 1;
-        List<List<Integer>> result = cs.combinationSum(candidates, target);
+        List<List<Integer>> result = CombinationSum.combinationSum(candidates, target);
 
         assertTrue(result.isEmpty());
     }
-
     @Test
     void testSingleElement() {
 
@@ -57,7 +47,6 @@ void testSingleElement() {
         assertEquals(1, result.size());
         assertTrue(result.contains(Arrays.asList(1)));
     }
-
     @Test
     void testSingleElementRepeated() {
 
@@ -68,7 +57,6 @@ void testSingleElementRepeated() {
         assertEquals(1, result.size());
         assertTrue(result.contains(Arrays.asList(2, 2, 2, 2)));
     }
-
     @Test
     void testLargerNumbers() {
 
@@ -83,7 +71,6 @@ void testLargerNumbers() {
             assertEquals(target, sum);
         }
     }
-
     @Test
     void testTargetZero() {
 
@@ -95,7 +82,6 @@ void testTargetZero() {
         assertEquals(1, result.size());
         assertTrue(result.get(0).isEmpty());
     }
-
     @Test
     void testEmptyCandidates() {
 
@@ -105,7 +91,6 @@ void testEmptyCandidates() {
 
         assertTrue(result.isEmpty());
     }
-
     @Test
     void testLargeTarget() {
         int[] candidates = {3, 5, 8};
@@ -121,7 +106,6 @@ void testLargeTarget() {
             assertEquals(target, sum);
         }
     }
-
     @Test
     void testAllCombinationsValid() {
         int[] candidates = {2, 3, 6, 7};