Add LowestSetBit (#5567)

This commit is contained in:
Prayas Kumar
2024-10-07 17:48:25 +05:30
committed by GitHub
parent 7f57fc92b4
commit 357fc6a271
2 changed files with 120 additions and 0 deletions

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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);
}
}

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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));
}
}