[ENHANCEMENT] Add Wavelet Tree Data Structure#7414
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space0032 wants to merge 3 commits intoTheAlgorithms:masterfrom
Open
[ENHANCEMENT] Add Wavelet Tree Data Structure#7414space0032 wants to merge 3 commits intoTheAlgorithms:masterfrom
space0032 wants to merge 3 commits intoTheAlgorithms:masterfrom
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space0032
requested review from
DenizAltunkapan,
alxkm and
yanglbme
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #7414 +/- ##
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+ Coverage 79.54% 79.61% +0.07%
- Complexity 7178 7218 +40
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Files 798 799 +1
Lines 23467 23572 +105
Branches 4617 4639 +22
============================================
+ Hits 18666 18767 +101
+ Misses 4055 4054 -1
- Partials 746 751 +5 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Pull request overview
This PR adds a new WaveletTree data structure under com.thealgorithms.datastructures.trees, providing rank, select, and kthSmallest (quantile) queries over an integer sequence, along with JUnit tests validating core behavior.
Changes:
- Introduces
WaveletTreeimplementation withrank(x, i),select(x, k), andkthSmallest(l, r, k). - Adds JUnit test suite covering typical cases, invalid inputs, empty/singleton arrays, and negative values.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.
| File | Description |
|---|---|
src/main/java/com/thealgorithms/datastructures/trees/WaveletTree.java |
Adds the Wavelet Tree implementation and query methods. |
src/test/java/com/thealgorithms/datastructures/trees/WaveletTreeTest.java |
Adds JUnit tests for rank/select/kthSmallest, including some edge cases. |
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| if (arr.length == 0 || low == high) { | ||
| return; | ||
| } | ||
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| int mid = low + (high - low) / 2; |
| if (node.low == node.high) { | ||
| return count; | ||
| } | ||
| int mid = node.low + (node.high - node.low) / 2; |
| if (node.low == node.high) { | ||
| return k - 1; // 0-based index within the imaginary array at the leaf | ||
| } | ||
| int mid = node.low + (node.high - node.low) / 2; |
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| if (root == null || left > right || left < 0 || k < 1 || k > right - left + 1) { | ||
| return -1; | ||
| } |
| if (arr == null || arr.length == 0) { | ||
| this.n = 0; | ||
| return; | ||
| } |
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| @Test | ||
| public void testKthSmallest() { | ||
| int[] arr = {5, 1, 2, 5, 1}; | ||
| WaveletTree wt = new WaveletTree(arr); | ||
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| // Array: [5, 1, 2, 5, 1] -> Sorted: [1, 1, 2, 5, 5] |
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Description
This Pull Request introduces the Wavelet Tree data structure to the
datastructures/treespackage in the repository. A Wavelet Tree is a highly efficient and versatile data structure used for compressed storage of sequences and answering complex range-based queries inO(log U)time.The main operations implemented are:
rank(x, i): Determines how many times the valuexappears from the beginning of the array up to the indexi.kthSmallest(l, r, k): Finds thek-th smallest element in the subarray[l, r].The functionality is generalized to handle large input arrays with an arbitrary range of values (
minValueandmaxValue).Files Added
WaveletTree.java: Contains the implementation of the Wavelet Tree data structure.WaveletTreeTest.java: Contains JUnit test cases to validate the correctness of the methods and handle edge cases.Complexity