Add Ones & Twos Complement in BitManipulation (TheAlgorithms#5604)

Author: Monk-AbhinayVerma

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

@@ -0,0 +1,28 @@
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * @author - https://github.com/Monk-AbhinayVerma
+ * @Wikipedia - https://en.wikipedia.org/wiki/Ones%27_complement
+ *            The class OnesComplement computes the complement of binary number
+ *            and returns
+ *            the complemented binary string.
+ * @return the complimented binary string
+ */
+public final class OnesComplement {
+    private OnesComplement() {
+    }
+
+    // Function to get the 1's complement of a binary number
+    public static String onesComplement(String binary) {
+        StringBuilder complement = new StringBuilder();
+        // Invert each bit to get the 1's complement
+        for (int i = 0; i < binary.length(); i++) {
+            if (binary.charAt(i) == '0') {
+                complement.append('1');
+            } else {
+                complement.append('0');
+            }
+        }
+        return complement.toString();
+    }
+}

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

@@ -0,0 +1,41 @@
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * @wikipedia - https://en.wikipedia.org/wiki/Two%27s_complement
+ *            This Algorithm was first suggested by Jon Von Neumann
+ * @author - https://github.com/Monk-AbhinayVerma
+ * @return the two's complement of any binary number
+ */
+public final class TwosComplement {
+    private TwosComplement() {
+    }
+
+    // Function to get the 2's complement of a binary number
+    public static String twosComplement(String binary) {
+        StringBuilder onesComplement = new StringBuilder();
+        // Step 1: Find the 1's complement (invert the bits)
+        for (int i = 0; i < binary.length(); i++) {
+            if (binary.charAt(i) == '0') {
+                onesComplement.append('1');
+            } else {
+                onesComplement.append('0');
+            }
+        }
+        // Step 2: Add 1 to the 1's complement
+        StringBuilder twosComplement = new StringBuilder(onesComplement);
+        boolean carry = true;
+        for (int i = onesComplement.length() - 1; i >= 0; i--) {
+            if (onesComplement.charAt(i) == '1' && carry) {
+                twosComplement.setCharAt(i, '0');
+            } else if (onesComplement.charAt(i) == '0' && carry) {
+                twosComplement.setCharAt(i, '1');
+                carry = false;
+            }
+        }
+        // If there is still a carry, append '1' at the beginning
+        if (carry) {
+            twosComplement.insert(0, '1');
+        }
+        return twosComplement.toString();
+    }
+}

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

@@ -0,0 +1,47 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test case for Highest Set Bit
+ * @author Abhinay Verma(https://github.com/Monk-AbhinayVerma)
+ */
+public class OnesComplementTest {
+
+    @Test
+    public void testOnesComplementAllZeroes() {
+
+        // Test cases with all-zero binary strings
+        assertEquals("1111", OnesComplement.onesComplement("0000"));
+        assertEquals("111", OnesComplement.onesComplement("000"));
+        assertEquals("11", OnesComplement.onesComplement("00"));
+        assertEquals("1", OnesComplement.onesComplement("0"));
+    }
+
+    @Test
+    public void testOnesComplementAllOnes() {
+        // Test cases with all-one binary strings
+        assertEquals("0000", OnesComplement.onesComplement("1111"));
+        assertEquals("000", OnesComplement.onesComplement("111"));
+        assertEquals("00", OnesComplement.onesComplement("11"));
+        assertEquals("0", OnesComplement.onesComplement("1"));
+    }
+
+    @Test
+    public void testOnesComplementMixedBits() {
+        // Test more mixed binary patterns
+        assertEquals("1010", OnesComplement.onesComplement("0101"));
+        assertEquals("0101", OnesComplement.onesComplement("1010"));
+        assertEquals("1100", OnesComplement.onesComplement("0011"));
+        assertEquals("0011", OnesComplement.onesComplement("1100"));
+        assertEquals("1001", OnesComplement.onesComplement("0110"));
+    }
+
+    @Test
+    public void testOnesComplementEmptyString() {
+        // Test empty string scenario
+        assertEquals("", OnesComplement.onesComplement(""));
+    }
+}

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

@@ -0,0 +1,54 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test case for Highest Set Bit
+ * @author Abhinay Verma(https://github.com/Monk-AbhinayVerma)
+ */
+public class TwosComplementTest {
+
+    @Test
+    public void testTwosComplementAllZeroes() {
+        // Test with a binary number consisting entirely of zeroes
+        assertEquals("10000", TwosComplement.twosComplement("0000"));
+        assertEquals("1000", TwosComplement.twosComplement("000"));
+        assertEquals("100", TwosComplement.twosComplement("00"));
+        assertEquals("10", TwosComplement.twosComplement("0"));
+    }
+
+    @Test
+    public void testTwosComplementAllOnes() {
+        // Test with a binary number consisting entirely of ones
+        assertEquals("00001", TwosComplement.twosComplement("11111"));
+        assertEquals("0001", TwosComplement.twosComplement("1111"));
+        assertEquals("001", TwosComplement.twosComplement("111"));
+        assertEquals("01", TwosComplement.twosComplement("11"));
+    }
+
+    @Test
+    public void testTwosComplementMixedBits() {
+        // Test with binary numbers with mixed bits
+        assertEquals("1111", TwosComplement.twosComplement("0001")); // 1's complement: 1110, then add 1: 1111
+        assertEquals("1001", TwosComplement.twosComplement("0111")); // 1's complement: 1000
+        assertEquals("11001", TwosComplement.twosComplement("00111")); // 1's complement: 11000, add 1: 11001
+        assertEquals("011", TwosComplement.twosComplement("101")); // 1's complement: 010, add 1: 011
+    }
+
+    @Test
+    public void testTwosComplementSingleBit() {
+        // Test with single bit
+        assertEquals("10", TwosComplement.twosComplement("0"));
+        assertEquals("1", TwosComplement.twosComplement("1"));
+    }
+
+    @Test
+    public void testTwosComplementWithLeadingZeroes() {
+        // Test with leading zeroes in the input
+        assertEquals("1111", TwosComplement.twosComplement("0001"));
+        assertEquals("101", TwosComplement.twosComplement("011"));
+        assertEquals("110", TwosComplement.twosComplement("010"));
+    }
+}