….2 (TheAlgorithms#7411)

Bumps [com.puppycrawl.tools:checkstyle](https://github.com/checkstyle/checkstyle) from 13.4.1 to 13.4.2.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-13.4.1...checkstyle-13.4.2)

---
updated-dependencies:
- dependency-name: com.puppycrawl.tools:checkstyle
  dependency-version: 13.4.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

fix: remove invalid reference [1] in Anagrams.java

Co-authored-by: Deniz Altunkapan <[email protected]>

* Optimized NQueens implementation using hashing

* Fixed checkstyle naming issues

* Fixed formatting issues

* Fixed operator wrap formatting

* Fixed formatting issues

* Fixed operator wrapping style

* Fixed print formatting

* Fixed print formatting

* Fixed operator formatting

* Removed extra brace

* feat: add Rat in a Maze backtracking algorithm with 10 unit tests

* test: add coverage for all-open maze and larger maze path

* style: apply clang-format fixes and add newline at end of files

* style: apply clang-format and checkstyle fixes

* Implement Wavelet Tree with rank and kthSmallest methods

* Implement Wavelet Tree with rank and kthSmallest methods

* Fix checkstyle multiple variable declarations violation

---------

Co-authored-by: Deniz Altunkapan <[email protected]>

…lgorithms#7423)

* Fix: remove floating Javadoc comments causing compilation error

* Docs: add Javadoc to CoinChange class and method

* Style: apply clang-format to CoinChange.java

…heAlgorithms#7425)

* fix: add null input validation to AlternativeStringArrange.arrange()

The arrange() method previously threw a NullPointerException when either
input string was null. This change explicitly validates the inputs and
throws IllegalArgumentException with a clear message, matching the
fail-fast pattern used by other utility classes in this package (e.g.
HammingDistance).

- Add null guard at the start of arrange()
- Update Javadoc with @throws and contract notes
- Add parameterized test covering all three null-input combinations

* fix: remove unused JUnit @test import (Checkstyle violation)

…hms#7431)

* chore(deps): bump org.junit:junit-bom from 6.0.3 to 6.1.0

Bumps [org.junit:junit-bom](https://github.com/junit-team/junit-framework) from 6.0.3 to 6.1.0.
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r6.0.3...r6.1.0)

---
updated-dependencies:
- dependency-name: org.junit:junit-bom
  dependency-version: 6.1.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

* style: resolve `DLS_DEAD_LOCAL_STORE` in `testIteratorEmptyBag`

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: vil02 <[email protected]>

)

* feat: add optimized Digit DP template and unit tests

* test: add test cases for max target sum and memoization hit to achieve 100% coverage

* style: fix indentation and code formatting for clang linter compliance

* fix: remove checkstyle inner assignment in solve method

* fix: remove checkstyle inner assignment in solve method -newline at end

…heAlgorithms#7428)

* feat(datastructures): add thread-safe bounded queue implementation

Implements a thread-safe blocking queue using ReentrantLock and
Condition variables for producer-consumer synchronization.

### What This Adds

**ThreadSafeQueue.java** - Thread-safe bounded queue:
- `enqueue()` - Blocking add to tail, waits when queue is full
- `dequeue()` - Blocking remove from head, waits when queue is empty
- `offer()` - Non-blocking add, returns false when full
- `poll()` - Non-blocking remove, returns null when empty
- `size()`, `isEmpty()`, `isFull()`, `capacity()` - State queries
- Uses circular buffer for O(1) enqueue/dequeue operations
- Supports multiple concurrent producers and consumers

**ThreadSafeQueueTest.java** - Comprehensive test suite:
- Basic enqueue/dequeue operations
- Offer/poll non-blocking behavior
- Null rejection validation
- Invalid capacity rejection
- Circular buffer wrap-around
- Multiple producers single consumer concurrency
- Single producer multiple consumers concurrency
- Blocking behavior verification
- Stress test with 8 concurrent threads

### Algorithm

Uses a circular buffer with ReentrantLock and two Condition variables:
- `notFull` - signaled when space becomes available
- `notEmpty` - signaled when items are added
- Producers await notFull when buffer is full
- Consumers await notEmpty when buffer is empty
- Signal opposite condition after each operation

Time: O(1) enqueue/dequeue | Space: O(n) bounded buffer

### Reference

https://en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem

* fix(datastructures): correct test capacity and simplify concurrent test

- testOfferPoll: Changed capacity from 3 to 2 so third offer correctly fails
- testMultipleProducersSingleConsumer: Removed startLatch, use dedicated
  consumer thread with synchronized results list for thread safety

* fix(datastructures): remove unused assertArrayEquals import

Checkstyle flagged UnusedImports violation for
org.junit.jupiter.api.Assertions.assertArrayEquals which was
not used in any test method.

* fix: replace signal() with signalAll() to satisfy SpotBugs MDM_SIGNAL_NOT_SIGNALALL

SpotBugs flags all four Condition.signal() calls in ThreadSafeQueue as Medium
severity bugs (MDM_SIGNAL_NOT_SIGNALALL). In a multi-producer/multi-consumer
scenario, signal() wakes only one waiting thread, which can cause deadlock when
multiple producers or consumers are blocked on the same condition variable.
Using signalAll() ensures all waiting threads are notified and can re-check
their loop condition, preventing the lost-wakeup problem that occurs when a
single signal wakes a thread that cannot make progress.

This change affects enqueue(), dequeue(), offer(), and poll() methods where
notEmpty.signal() and notFull.signal() are replaced with notEmpty.signalAll()
and notFull.signalAll() respectively.

* test: replace static imports with Assertions prefix to satisfy PMD TooManyStaticImports

PMD flags TooManyStaticImports when more than 4 static imports are present.
The test file had 5 static imports from org.junit.jupiter.api.Assertions
(equals, assertFalse, assertNull, assertThrows, assertTrue) which exceeded
the default threshold. Replaced with regular import and Assertions.
prefix to eliminate the PMD violation while maintaining readability.

…ep explanation (TheAlgorithms#7435)

…from 3.5.5 to 3.5.6 (TheAlgorithms#7436)

chore(deps-dev): bump org.apache.maven.plugins:maven-surefire-plugin

Bumps [org.apache.maven.plugins:maven-surefire-plugin](https://github.com/apache/maven-surefire) from 3.5.5 to 3.5.6.
- [Release notes](https://github.com/apache/maven-surefire/releases)
- [Commits](apache/maven-surefire@surefire-3.5.5...surefire-3.5.6)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-surefire-plugin
  dependency-version: 3.5.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

….0 (TheAlgorithms#7441)

Bumps [com.puppycrawl.tools:checkstyle](https://github.com/checkstyle/checkstyle) from 13.4.2 to 13.5.0.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-13.4.2...checkstyle-13.5.0)

---
updated-dependencies:
- dependency-name: com.puppycrawl.tools:checkstyle
  dependency-version: 13.5.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

…ests (TheAlgorithms#7445)

* test: upgrade MergeSortedArrayListTest to use JUnit 5 parameterized tests

* style: strip trailing whitespace and add trailing newline via IDE

* style: align layout with clang-format rules

* style: collapse stream arguments to single lines for clang

* style: fix line wrapping length for clang linter

---------

Co-authored-by: psawale <[email protected]>

…ss (TheAlgorithms#7427)

* feat(matrix): add QR decomposition algorithm using Gram-Schmidt process

Decomposes a matrix A into an orthogonal matrix Q and an upper triangular
matrix R such that A = Q * R.

### What This Adds

**QRDecomposition.java** - Main algorithm implementation:
- `decompose()` - Performs QR factorization using the Gram-Schmidt process
- Returns a QR object containing both Q (orthogonal) and R (upper triangular) matrices
- Validates input matrix using MatrixUtil.validateInputMatrix()
- Throws ArithmeticException for rank-deficient matrices

**QRDecompositionTest.java** - Unit tests:
- Tests for 2x2 and 3x3 matrix decomposition
- Verifies Q * R reconstruction equals original matrix
- Validates Q columns are orthonormal
- Confirms R is upper triangular
- Tests identity matrix decomposition
- Tests rank-deficient matrix rejection
- Tests null and empty matrix rejection

### Algorithm

The Gram-Schmidt process orthogonalizes columns iteratively:
- For each column j, subtract projections onto previous orthogonal vectors
- Normalize to get j-th column of Q
- Store coefficients in R[i][j]

Time: O(m*n^2) | Space: O(m*n + n^2)

### Reference

https://en.wikipedia.org/wiki/QR_decomposition

* fix(matrix): inline matrix validation to avoid cross-package dependency

MatrixUtil is in com.thealgorithms.matrix.utils package which causes
compilation errors when referenced from com.thealgorithms.matrix.
Inlined the validation logic (validateInputMatrix, hasValidRows,
isJaggedMatrix) directly into QRDecomposition to resolve the issue.