Added BitwiseGCD.java and BitwiseGCDTest.java (#6545)

2025-12-19 07:00:35 +08:00 · 2025-09-27 16:32:34 +05:30
parent 09cacae1c3
commit fb12971fd6
2 changed files with 257 additions and 0 deletions
--- a/src/test/java/com/thealgorithms/bitmanipulation/BitwiseGCDTest.java
+++ b/src/test/java/com/thealgorithms/bitmanipulation/BitwiseGCDTest.java
@@ -0,0 +1,110 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.math.BigInteger;
+import org.junit.jupiter.api.Test;
+
+public class BitwiseGCDTest {
+
+    @Test
+    public void testGcdBasic() {
+        assertEquals(6L, BitwiseGCD.gcd(48L, 18L));
+    }
+
+    @Test
+    public void testGcdZeroAndNonZero() {
+        assertEquals(5L, BitwiseGCD.gcd(0L, 5L));
+        assertEquals(5L, BitwiseGCD.gcd(5L, 0L));
+    }
+
+    @Test
+    public void testGcdBothZero() {
+        assertEquals(0L, BitwiseGCD.gcd(0L, 0L));
+    }
+
+    @Test
+    public void testGcdNegativeInputs() {
+        assertEquals(6L, BitwiseGCD.gcd(-48L, 18L));
+        assertEquals(6L, BitwiseGCD.gcd(48L, -18L));
+        assertEquals(6L, BitwiseGCD.gcd(-48L, -18L));
+    }
+
+    @Test
+    public void testGcdIntOverload() {
+        assertEquals(6, BitwiseGCD.gcd(48, 18));
+    }
+
+    @Test
+    public void testGcdArray() {
+        long[] values = {48L, 18L, 6L};
+        assertEquals(6L, BitwiseGCD.gcd(values));
+    }
+
+    @Test
+    public void testGcdEmptyArray() {
+        long[] empty = {};
+        assertEquals(0L, BitwiseGCD.gcd(empty));
+    }
+
+    @Test
+    public void testGcdCoprime() {
+        assertEquals(1L, BitwiseGCD.gcd(17L, 13L));
+    }
+
+    @Test
+    public void testGcdPowersOfTwo() {
+        assertEquals(1024L, BitwiseGCD.gcd(1L << 20, 1L << 10));
+    }
+
+    @Test
+    public void testGcdLargeNumbers() {
+        assertEquals(6L, BitwiseGCD.gcd(270L, 192L));
+    }
+
+    @Test
+    public void testGcdEarlyExitArray() {
+        long[] manyCoprimes = {7L, 11L, 13L, 17L, 19L, 23L, 29L};
+        assertEquals(1L, BitwiseGCD.gcd(manyCoprimes));
+    }
+
+    @Test
+    public void testGcdSameNumbers() {
+        assertEquals(42L, BitwiseGCD.gcd(42L, 42L));
+    }
+
+    @Test
+    public void testGcdLongMinValueBigInteger() {
+        // gcd(Long.MIN_VALUE, 0) = |Long.MIN_VALUE| = 2^63; must use BigInteger to represent it
+        BigInteger expected = BigInteger.ONE.shiftLeft(63); // 2^63
+        assertEquals(expected, BitwiseGCD.gcdBig(Long.MIN_VALUE, 0L));
+    }
+
+    @Test
+    public void testGcdLongMinValueLongOverloadThrows() {
+        // The long overload cannot return 2^63 as a positive signed long, so it must throw
+        assertThrows(ArithmeticException.class, () -> BitwiseGCD.gcd(Long.MIN_VALUE, 0L));
+    }
+
+    @Test
+    public void testGcdWithLongMinAndOther() {
+        // gcd(Long.MIN_VALUE, 2^10) should be 2^10
+        long p = 1L << 10;
+        BigInteger expected = BigInteger.valueOf(p);
+        assertEquals(expected, BitwiseGCD.gcdBig(Long.MIN_VALUE, p));
+    }
+
+    @Test
+    public void testGcdWithBothLongMin() {
+        // gcd(Long.MIN_VALUE, Long.MIN_VALUE) = 2^63
+        BigInteger expected = BigInteger.ONE.shiftLeft(63);
+        assertEquals(expected, BitwiseGCD.gcdBig(Long.MIN_VALUE, Long.MIN_VALUE));
+    }
+
+    @Test
+    public void testGcdEdgeCasesMixed() {
+        assertEquals(1L, BitwiseGCD.gcd(1L, Long.MAX_VALUE));
+        assertEquals(1L, BitwiseGCD.gcd(Long.MAX_VALUE, 1L));
+    }
+}