Add LowestSetBit (#5567)

Author: prayas7102

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

@@ -0,0 +1,34 @@
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * Lowest Set Bit
+ * @author Prayas Kumar (https://github.com/prayas7102)
+ */
+
+public final class LowestSetBit {
+    // Private constructor to hide the default public one
+    private LowestSetBit() {
+    }
+    /**
+     * Isolates the lowest set bit of the given number. For example, if n = 18
+     * (binary: 10010), the result will be 2 (binary: 00010).
+     *
+     * @param n the number whose lowest set bit will be isolated
+     * @return the isolated lowest set bit of n
+     */
+    public static int isolateLowestSetBit(int n) {
+        // Isolate the lowest set bit using n & -n
+        return n & -n;
+    }
+    /**
+     * Clears the lowest set bit of the given number.
+     * For example, if n = 18 (binary: 10010), the result will be 16 (binary: 10000).
+     *
+     * @param n the number whose lowest set bit will be cleared
+     * @return the number after clearing its lowest set bit
+     */
+    public static int clearLowestSetBit(int n) {
+        // Clear the lowest set bit using n & (n - 1)
+        return n & (n - 1);
+    }
+}

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

@@ -0,0 +1,86 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test case for Lowest Set Bit
+ * @author Prayas Kumar (https://github.com/prayas7102)
+ */
+
+public class LowestSetBitTest {
+
+    @Test
+    void testLowestSetBitWithPositiveNumber() {
+        // Test with a general positive number
+        assertEquals(2, LowestSetBit.isolateLowestSetBit(18)); // 18 in binary: 10010, lowest bit is 2
+    }
+
+    @Test
+    void testLowestSetBitWithZero() {
+        // Test with zero (edge case, no set bits)
+        assertEquals(0, LowestSetBit.isolateLowestSetBit(0)); // 0 has no set bits, result should be 0
+    }
+
+    @Test
+    void testLowestSetBitWithOne() {
+        // Test with number 1 (lowest set bit is 1 itself)
+        assertEquals(1, LowestSetBit.isolateLowestSetBit(1)); // 1 in binary: 0001, lowest bit is 1
+    }
+
+    @Test
+    void testLowestSetBitWithPowerOfTwo() {
+        // Test with a power of two (only one set bit)
+        assertEquals(16, LowestSetBit.isolateLowestSetBit(16)); // 16 in binary: 10000, lowest bit is 16
+    }
+
+    @Test
+    void testLowestSetBitWithAllBitsSet() {
+        // Test with a number with multiple set bits (like 7)
+        assertEquals(1, LowestSetBit.isolateLowestSetBit(7)); // 7 in binary: 111, lowest bit is 1
+    }
+
+    @Test
+    void testLowestSetBitWithNegativeNumber() {
+        // Test with a negative number (-1 in two's complement has all bits set)
+        assertEquals(1, LowestSetBit.isolateLowestSetBit(-1)); // -1 in two's complement is all 1s, lowest bit is 1
+    }
+
+    @Test
+    void testLowestSetBitWithLargeNumber() {
+        // Test with a large number
+        assertEquals(64, LowestSetBit.isolateLowestSetBit(448)); // 448 in binary: 111000000, lowest bit is 64
+    }
+
+    @Test
+    void testClearLowestSetBitFor18() {
+        // n = 18 (binary: 10010), expected result = 16 (binary: 10000)
+        assertEquals(16, LowestSetBit.clearLowestSetBit(18));
+    }
+
+    @Test
+    void testClearLowestSetBitFor10() {
+        // n = 10 (binary: 1010), expected result = 8 (binary: 1000)
+        assertEquals(8, LowestSetBit.clearLowestSetBit(10));
+    }
+
+    @Test
+    void testClearLowestSetBitFor7() {
+        // n = 7 (binary: 0111), expected result = 6 (binary: 0110)
+        assertEquals(6, LowestSetBit.clearLowestSetBit(7));
+    }
+
+    @Test
+    void testClearLowestSetBitFor0() {
+        // n = 0 (binary: 0000), no set bits to clear, expected result = 0
+        assertEquals(0, LowestSetBit.clearLowestSetBit(0));
+    }
+
+    @Test
+    void testClearLowestSetBitForNegativeNumber() {
+        // Test negative number to see how it behaves with two's complement
+        // n = -1 (binary: all 1s in two's complement), expected result = -2 (clearing lowest set bit)
+        assertEquals(-2, LowestSetBit.clearLowestSetBit(-1));
+    }
+}