From eba6823c3ad8f81fac5ae1f4cc3de217063fd606 Mon Sep 17 00:00:00 2001 From: Hardik Pawar <97388607+Hardvan@users.noreply.github.com> Date: Sat, 12 Oct 2024 12:15:28 +0530 Subject: [PATCH] Add `HigherLowerPowerOfTwo` algorithm (#5707) --- DIRECTORY.md | 2 + .../HigherLowerPowerOfTwo.java | 54 +++++++++++++++++++ .../HigherLowerPowerOfTwoTest.java | 26 +++++++++ 3 files changed, 82 insertions(+) create mode 100644 src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java create mode 100644 src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java diff --git a/DIRECTORY.md b/DIRECTORY.md index b62cde038..880a5f12b 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -30,6 +30,7 @@ * [CountSetBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/CountSetBits.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) * [HighestSetBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/HighestSetBit.java) * [IndexOfRightMostSetBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/IndexOfRightMostSetBit.java) * [IsEven](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/IsEven.java) @@ -658,6 +659,7 @@ * [CountSetBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/CountSetBitsTest.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) * [HighestSetBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/HighestSetBitTest.java) * [IndexOfRightMostSetBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/IndexOfRightMostSetBitTest.java) * [IsEvenTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/IsEvenTest.java) diff --git a/src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java b/src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java new file mode 100644 index 000000000..0fb058b2b --- /dev/null +++ b/src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java @@ -0,0 +1,54 @@ +package com.thealgorithms.bitmanipulation; + +/** + * HigherLowerPowerOfTwo class has two methods to find the next higher and lower power of two. + *

+ * nextHigherPowerOfTwo method finds the next higher power of two. + * nextLowerPowerOfTwo method finds the next lower power of two. + * Both methods take an integer as input and return the next higher or lower power of two. + * If the input is less than 1, the next higher power of two is 1. + * If the input is less than or equal to 1, the next lower power of two is 0. + * nextHigherPowerOfTwo method uses bitwise operations to find the next higher power of two. + * nextLowerPowerOfTwo method uses Integer.highestOneBit method to find the next lower power of two. + * The time complexity of both methods is O(1). + * The space complexity of both methods is O(1). + *

+ * + * @author Hardvan + */ +public final class HigherLowerPowerOfTwo { + private HigherLowerPowerOfTwo() { + } + + /** + * Finds the next higher power of two. + * + * @param x The given number. + * @return The next higher power of two. + */ + public static int nextHigherPowerOfTwo(int x) { + if (x < 1) { + return 1; + } + x--; + x |= x >> 1; + x |= x >> 2; + x |= x >> 4; + x |= x >> 8; + x |= x >> 16; + return x + 1; + } + + /** + * Finds the next lower power of two. + * + * @param x The given number. + * @return The next lower power of two. + */ + public static int nextLowerPowerOfTwo(int x) { + if (x < 1) { + return 0; + } + return Integer.highestOneBit(x); + } +} diff --git a/src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java b/src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java new file mode 100644 index 000000000..343910029 --- /dev/null +++ b/src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java @@ -0,0 +1,26 @@ +package com.thealgorithms.bitmanipulation; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import org.junit.jupiter.api.Test; + +public class HigherLowerPowerOfTwoTest { + + @Test + public void testNextHigherPowerOfTwo() { + assertEquals(32, HigherLowerPowerOfTwo.nextHigherPowerOfTwo(19)); // next higher power of two is 32 + assertEquals(1, HigherLowerPowerOfTwo.nextHigherPowerOfTwo(1)); // next higher power of two is 1 + assertEquals(16, HigherLowerPowerOfTwo.nextHigherPowerOfTwo(15)); // next higher power of two is 16 + assertEquals(8, HigherLowerPowerOfTwo.nextHigherPowerOfTwo(8)); // next higher power of two is 8 + assertEquals(16, HigherLowerPowerOfTwo.nextHigherPowerOfTwo(9)); // next higher power of two is 16 + } + + @Test + public void testNextLowerPowerOfTwo() { + assertEquals(16, HigherLowerPowerOfTwo.nextLowerPowerOfTwo(19)); // next lower power of two is 16 + assertEquals(1, HigherLowerPowerOfTwo.nextLowerPowerOfTwo(1)); // next lower power of two is 1 + assertEquals(8, HigherLowerPowerOfTwo.nextLowerPowerOfTwo(9)); // next lower power of two is 8 + assertEquals(8, HigherLowerPowerOfTwo.nextLowerPowerOfTwo(15)); // next lower power of two is 8 + assertEquals(8, HigherLowerPowerOfTwo.nextLowerPowerOfTwo(8)); // next lower power of two is 8 + } +}