Add GenerateSubsets algorithm (#5867)

Author: Hardvan

DIRECTORY.md

@@ -32,6 +32,7 @@
             * [CountSetBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/CountSetBits.java)
             * [FindNthBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/FindNthBit.java)
             * [FirstDifferentBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/FirstDifferentBit.java)
+            * [GenerateSubsets](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/GenerateSubsets.java)
             * [GrayCodeConversion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/GrayCodeConversion.java)
             * [HammingDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/HammingDistance.java)
             * [HigherLowerPowerOfTwo](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java)
@@ -738,6 +739,7 @@
             * [CountSetBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/CountSetBitsTest.java)
             * [FindNthBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/FindNthBitTest.java)
             * [FirstDifferentBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/FirstDifferentBitTest.java)
+            * [GenerateSubsetsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/GenerateSubsetsTest.java)
             * [GrayCodeConversionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/GrayCodeConversionTest.java)
             * [HammingDistanceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/HammingDistanceTest.java)
             * [HigherLowerPowerOfTwoTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java)

src/main/java/com/thealgorithms/bitmanipulation/GenerateSubsets.java

@@ -0,0 +1,44 @@
+package com.thealgorithms.bitmanipulation;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class provides a method to generate all subsets (power set)
+ * of a given set using bit manipulation.
+ *
+ * @author Hardvan
+ */
+public final class GenerateSubsets {
+    private GenerateSubsets() {
+    }
+
+    /**
+     * Generates all subsets of a given set using bit manipulation.
+     * Steps:
+     * 1. Iterate over all numbers from 0 to 2^n - 1.
+     * 2. For each number, iterate over all bits from 0 to n - 1.
+     * 3. If the i-th bit of the number is set, add the i-th element of the set to the current subset.
+     * 4. Add the current subset to the list of subsets.
+     * 5. Return the list of subsets.
+     *
+     * @param set the input set of integers
+     * @return a list of all subsets represented as lists of integers
+     */
+    public static List<List<Integer>> generateSubsets(int[] set) {
+        int n = set.length;
+        List<List<Integer>> subsets = new ArrayList<>();
+
+        for (int mask = 0; mask < (1 << n); mask++) {
+            List<Integer> subset = new ArrayList<>();
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) != 0) {
+                    subset.add(set[i]);
+                }
+            }
+            subsets.add(subset);
+        }
+
+        return subsets;
+    }
+}

src/test/java/com/thealgorithms/bitmanipulation/GenerateSubsetsTest.java

@@ -0,0 +1,52 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class GenerateSubsetsTest {
+
+    @Test
+    void testGenerateSubsetsWithTwoElements() {
+        int[] set = {1, 2};
+        List<List<Integer>> expected = new ArrayList<>();
+        expected.add(new ArrayList<>());
+        expected.add(Arrays.asList(1));
+        expected.add(Arrays.asList(2));
+        expected.add(Arrays.asList(1, 2));
+
+        List<List<Integer>> result = GenerateSubsets.generateSubsets(set);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testGenerateSubsetsWithOneElement() {
+        int[] set = {3};
+        List<List<Integer>> expected = new ArrayList<>();
+        expected.add(new ArrayList<>());
+        expected.add(Arrays.asList(3));
+
+        List<List<Integer>> result = GenerateSubsets.generateSubsets(set);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testGenerateSubsetsWithThreeElements() {
+        int[] set = {4, 5, 6};
+        List<List<Integer>> expected = new ArrayList<>();
+        expected.add(new ArrayList<>());
+        expected.add(Arrays.asList(4));
+        expected.add(Arrays.asList(5));
+        expected.add(Arrays.asList(4, 5));
+        expected.add(Arrays.asList(6));
+        expected.add(Arrays.asList(4, 6));
+        expected.add(Arrays.asList(5, 6));
+        expected.add(Arrays.asList(4, 5, 6));
+
+        List<List<Integer>> result = GenerateSubsets.generateSubsets(set);
+        assertEquals(expected, result);
+    }
+}