From 38df2cc74c3731c3d0d18139ad46389e4bccc27b Mon Sep 17 00:00:00 2001 From: Hardik Pawar Date: Tue, 15 Oct 2024 12:33:09 +0530 Subject: [PATCH 1/5] feat: Add `MergeKSortedArrays` new algorithm with Junit tests --- .../heaps/MergeKSortedArrays.java | 60 +++++++++++++++++++ .../heaps/MergeKSortedArraysTest.java | 53 ++++++++++++++++ 2 files changed, 113 insertions(+) create mode 100644 src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java create mode 100644 src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java diff --git a/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java b/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java new file mode 100644 index 000000000000..e41711f05914 --- /dev/null +++ b/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java @@ -0,0 +1,60 @@ +package com.thealgorithms.datastructures.heaps; + +import java.util.Comparator; +import java.util.PriorityQueue; + +/** + * This class provides a method to merge multiple sorted arrays into a single sorted array. + * It utilizes a min-heap to efficiently retrieve the smallest elements from each array. + * + * Time Complexity: O(n * log k), where n is the total number of elements across all arrays + * and k is the number of arrays. + * + * Space Complexity: O(k) for the heap, where k is the number of arrays. + * + * @author Hardvan + */ +public final class MergeKSortedArrays { + private MergeKSortedArrays() { + } + + /** + * Merges k sorted arrays into one sorted array using a min-heap. + * Steps: + * 1. Create a min-heap to store elements in the format: {value, array index, element index} + * 2. Add the first element from each array to the heap + * 3. While the heap is not empty, remove the smallest element from the heap + * and add it to the result array. If there are more elements in the same array, + * add the next element to the heap. + * Continue until all elements have been processed. + * The result array will contain all elements in sorted order. + * 4. Return the result array. + * + * @param arrays a 2D array, where each subarray is sorted in non-decreasing order + * @return a single sorted array containing all elements from the input arrays + */ + public static int[] mergeKArrays(int[][] arrays) { + PriorityQueue minHeap = new PriorityQueue<>(Comparator.comparingInt(a -> a[0])); + + int totalLength = 0; + for (int i = 0; i < arrays.length; i++) { + if (arrays[i].length > 0) { + minHeap.offer(new int[] {arrays[i][0], i, 0}); + totalLength += arrays[i].length; + } + } + + int[] result = new int[totalLength]; + int index = 0; + while (!minHeap.isEmpty()) { + int[] top = minHeap.poll(); + result[index++] = top[0]; + + if (top[2] + 1 < arrays[top[1]].length) { + minHeap.offer(new int[] {arrays[top[1]][top[2] + 1], top[1], top[2] + 1}); + } + } + + return result; + } +} diff --git a/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java b/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java new file mode 100644 index 000000000000..bbef0a40b60b --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java @@ -0,0 +1,53 @@ +package com.thealgorithms.datastructures.heaps; + +import static org.junit.jupiter.api.Assertions.assertArrayEquals; + +import java.util.stream.Stream; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.Arguments; +import org.junit.jupiter.params.provider.MethodSource; + +public class MergeKSortedArraysTest { + + /** + * Parameterized test for merging multiple sorted arrays. + * Each test case provides input arrays and the expected merged output. + * + * @param arrays the input 2D array of sorted arrays + * @param expected the expected merged sorted array + */ + @ParameterizedTest + @MethodSource("provideTestCases") + public void testMergeKArrays(int[][] arrays, int[] expected) { + assertArrayEquals(expected, MergeKSortedArrays.mergeKArrays(arrays)); + } + + /** + * Provides various test cases including edge cases for merging sorted arrays. + * + * @return a stream of test arguments containing input arrays and expected outputs + */ + private static Stream provideTestCases() { + return Stream.of( + // Basic test case with multiple arrays + Arguments.of(new int[][] {{1, 4, 5}, {1, 3, 4}, {2, 6}}, new int[] {1, 1, 2, 3, 4, 4, 5, 6}), + + // Edge case: All arrays are empty + Arguments.of(new int[][] {{}, {}, {}}, new int[] {}), + + // Edge case: One array is empty + Arguments.of(new int[][] {{1, 3, 5}, {}, {2, 4, 6}}, new int[] {1, 2, 3, 4, 5, 6}), + + // Single array + Arguments.of(new int[][] {{1, 2, 3}}, new int[] {1, 2, 3}), + + // Arrays with negative numbers + Arguments.of(new int[][] {{-5, 1, 3}, {-10, 0, 2}}, new int[] {-10, -5, 0, 1, 2, 3}), + + // Arrays with duplicate elements + Arguments.of(new int[][] {{1, 1, 2}, {1, 3, 3}, {2, 2, 4}}, new int[] {1, 1, 1, 2, 2, 2, 3, 3, 4}), + + // Edge case: Arrays of varying lengths + Arguments.of(new int[][] {{1, 2}, {3}, {4, 5, 6, 7}}, new int[] {1, 2, 3, 4, 5, 6, 7})); + } +} From fd8d709a2df458e0e85676a0d844b2bb931c1d11 Mon Sep 17 00:00:00 2001 From: Hardvan Date: Tue, 15 Oct 2024 07:03:28 +0000 Subject: [PATCH 2/5] Update directory --- DIRECTORY.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/DIRECTORY.md b/DIRECTORY.md index 6073904a745e..bc292efab092 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -169,6 +169,7 @@ * [HeapElement](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/HeapElement.java) * [LeftistHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/LeftistHeap.java) * [MaxHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MaxHeap.java) + * [MergeKSortedArrays](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java) * [MinHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MinHeap.java) * [MinPriorityQueue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MinPriorityQueue.java) * lists @@ -802,6 +803,7 @@ * heaps * [FibonacciHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/FibonacciHeapTest.java) * [LeftistHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/LeftistHeapTest.java) + * [MergeKSortedArraysTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java) * lists * [CircleLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CircleLinkedListTest.java) * [CreateAndDetectLoopTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CreateAndDetectLoopTest.java) From df5525a88f9f91f35baed75c4ff9b7b3261f6f9a Mon Sep 17 00:00:00 2001 From: Hardik Pawar Date: Tue, 15 Oct 2024 12:41:07 +0530 Subject: [PATCH 3/5] Fix --- .../datastructures/heaps/MergeKSortedArraysTest.java | 12 ------------ 1 file changed, 12 deletions(-) diff --git a/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java b/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java index bbef0a40b60b..c9b754619286 100644 --- a/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java +++ b/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java @@ -9,24 +9,12 @@ public class MergeKSortedArraysTest { - /** - * Parameterized test for merging multiple sorted arrays. - * Each test case provides input arrays and the expected merged output. - * - * @param arrays the input 2D array of sorted arrays - * @param expected the expected merged sorted array - */ @ParameterizedTest @MethodSource("provideTestCases") public void testMergeKArrays(int[][] arrays, int[] expected) { assertArrayEquals(expected, MergeKSortedArrays.mergeKArrays(arrays)); } - /** - * Provides various test cases including edge cases for merging sorted arrays. - * - * @return a stream of test arguments containing input arrays and expected outputs - */ private static Stream provideTestCases() { return Stream.of( // Basic test case with multiple arrays From 9e2bb3a57072ec39de9c6fd8ba415305259da0eb Mon Sep 17 00:00:00 2001 From: Hardvan Date: Sat, 26 Oct 2024 09:38:42 +0000 Subject: [PATCH 4/5] Update directory --- DIRECTORY.md | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/DIRECTORY.md b/DIRECTORY.md index a195e5b1ceb9..d6936e6fd680 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -177,11 +177,8 @@ * [KthElementFinder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/KthElementFinder.java) * [LeftistHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/LeftistHeap.java) * [MaxHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MaxHeap.java) - - * [MergeKSortedArrays](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java) - * [MedianFinder](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MedianFinder.java) - + * [MergeKSortedArrays](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MergeKSortedArrays.java) * [MinHeap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MinHeap.java) * [MinPriorityQueue](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/heaps/MinPriorityQueue.java) * lists @@ -856,11 +853,8 @@ * [GenericHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/GenericHeapTest.java) * [KthElementFinderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/KthElementFinderTest.java) * [LeftistHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/LeftistHeapTest.java) - - * [MergeKSortedArraysTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java) - * [MedianFinderTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MedianFinderTest.java) - + * [MergeKSortedArraysTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MergeKSortedArraysTest.java) * [MinPriorityQueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MinPriorityQueueTest.java) * lists * [CircleLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CircleLinkedListTest.java) From 2563b865478a08d614618da1f276626a4c0f5eeb Mon Sep 17 00:00:00 2001 From: siriak Date: Sat, 26 Oct 2024 11:58:14 +0000 Subject: [PATCH 5/5] Update directory --- DIRECTORY.md | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/DIRECTORY.md b/DIRECTORY.md index 4b634a79b3b8..7471b482d500 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -321,6 +321,8 @@ * [BresenhamLine](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/BresenhamLine.java) * [ConvexHull](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/ConvexHull.java) * [GrahamScan](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/GrahamScan.java) + * [MidpointCircle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/MidpointCircle.java) + * [MidpointEllipse](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/MidpointEllipse.java) * [Point](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/geometry/Point.java) * graph * [StronglyConnectedComponentOptimized](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/graph/StronglyConnectedComponentOptimized.java) @@ -361,6 +363,7 @@ * [Average](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/Average.java) * [BinaryPow](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/BinaryPow.java) * [BinomialCoefficient](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/BinomialCoefficient.java) + * [CatalanNumbers](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/CatalanNumbers.java) * [Ceil](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/Ceil.java) * [ChineseRemainderTheorem](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/ChineseRemainderTheorem.java) * [CircularConvolutionFFT](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/CircularConvolutionFFT.java) @@ -969,6 +972,8 @@ * [BresenhamLineTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/BresenhamLineTest.java) * [ConvexHullTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/ConvexHullTest.java) * [GrahamScanTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/GrahamScanTest.java) + * [MidpointCircleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/MidpointCircleTest.java) + * [MidpointEllipseTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/MidpointEllipseTest.java) * graph * [StronglyConnectedComponentOptimizedTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/graph/StronglyConnectedComponentOptimizedTest.java) * greedyalgorithms @@ -1005,6 +1010,7 @@ * [AverageTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/AverageTest.java) * [BinaryPowTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/BinaryPowTest.java) * [BinomialCoefficientTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/BinomialCoefficientTest.java) + * [CatalanNumbersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CatalanNumbersTest.java) * [CeilTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CeilTest.java) * [ChineseRemainderTheoremTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/ChineseRemainderTheoremTest.java) * [CollatzConjectureTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/CollatzConjectureTest.java)