BAEL-7357 Code for the Find Equilibrium Indexes of an Array

core-java-modules/core-java-arrays-operations-advanced-2/src/main/java/com/baeldung/equilibriumindex/EquilibriumIndexFinder.java

@@ -0,0 +1,24 @@
+package com.baeldung.equilibriumindex;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class EquilibriumIndexFinder {
+    
+    List<Integer> findEquilibriumIndexes(int[] array) {
+        int[] partialSums = new int[array.length + 1];
+        partialSums[0] = 0;
+        for (int i=0; i<array.length; i++) {
+            partialSums[i+1] = partialSums[i] + array[i]; 
+        }
+        
+        List<Integer> equilibriumIndexes = new ArrayList<Integer>();
+        for (int i=0; i<array.length; i++) {
+            if (partialSums[i] == (partialSums[array.length] - (partialSums[i+1]))) {
+                equilibriumIndexes.add(i);
+            }
+        }
+        return equilibriumIndexes;
+    }
+
+}

core-java-modules/core-java-arrays-operations-advanced-2/src/test/java/com/baeldung/equilibriumindex/EquilibriumIndexFinderUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.equilibriumindex;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class EquilibriumIndexFinderUnitTest {
+    
+    @Test
+    void givenArrayHasEquilibriumIndexes_whenFindEquilibriumIndexes_thenListAllEquilibriumIndexes() {
+        int[] array = {1, -3, 0, 4, -5, 4, 0, 1, -2, -1};
+        assertThat(new EquilibriumIndexFinder().findEquilibriumIndexes(array)).containsExactly(1, 4, 9);
+    }
+   
+    @Test
+    void givenArrayWithoutEquilibriumIndexes_whenFindEquilibriumIndexes_thenEmptyList() {
+        int[] array = {1, 2, 3};
+        assertThat(new EquilibriumIndexFinder().findEquilibriumIndexes(array)).isEmpty();
+    }
+   
+    @Test
+    void givenArrayWithOneElement_whenFindEquilibriumIndexes_thenListFirstIndex() {
+        int[] array = {5};
+        assertThat(new EquilibriumIndexFinder().findEquilibriumIndexes(array)).containsExactly(0);
+    }
+
+}