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Add stack-queue module: ten stack and queue interview problems, monotonic stack, min stack, queue from stacks and stack from a queue, brute-force cross-checks, dry-run traces, operation counts, pitfalls (11 tests)

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Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b6nxynun5JFivebVb1
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# stack-queue
Companion code for the ankurm.com article **Stack and Queue Problems in Java: Balanced Parentheses, Next Greater Element, Min Stack**.
Ten classic interview problems on stacks and queues, each cross-checked against an obviously-correct
brute-force version on seeded random inputs. Every figure and console line in the article is quoted from a
file in `output/`, which the JUnit tests write while asserting the same numbers. There is no `docs/` folder:
the explanations live in the article itself.
## Versions
| Component | Version | Verified against |
|---|---|---|
| JDK | Temurin 25.0.5+8 (LTS) | `java -version` |
| JUnit | 6.1.3 | `junit-bom` `maven-metadata.xml` on Maven Central (latest GA) |
| Maven | 3.9.x | `mvn -version` |
## Quickstart
```bash
cd stack-queue
export JAVA_HOME=/path/to/jdk-25 PATH="$JAVA_HOME/bin:$PATH"
./scripts/run-all.sh # runs 11 tests and regenerates output/*.txt
```
The first Maven run must be online so the plugins land in the local cache.
## The ten problems
| # | Problem | Idea | Method |
|---|---|---|---|
| 1 | Balanced parentheses | stack of expected closers | `Parentheses.isBalanced` |
| 2 | Evaluate Reverse Polish Notation | stack of operands | `Rpn.evaluate` |
| 3 | Min stack | second stack, or one stack of differences | `MinStack`, `EncodedMinStack` |
| 4 | Next greater element | monotonic stack | `MonotonicStack.nextGreater`, `nextGreaterSubset` |
| 5 | Daily temperatures | monotonic stack of indices | `MonotonicStack.dailyTemperatures` |
| 6 | Next greater element, circular | monotonic stack, two laps | `MonotonicStack.nextGreaterCircular` |
| 7 | Largest rectangle in a histogram | monotonic stack with a sentinel | `MonotonicStack.largestRectangle` |
| 8 | Decode string | stack of parked text and counts | `DecodeString.decode` |
| 9 | Queue using two stacks | pour only when the output stack is empty | `QueueViaStacks` |
| 10 | Stack using one queue | rotate after every push | `StackViaQueue` |
## Source layout
```
stack-queue/
├── pom.xml
├── scripts/run-all.sh
├── src/main/java/com/ankurm/interviewlab/stackqueue/
│ ├── Parentheses.java, Rpn.java, DecodeString.java problems 1, 2, 8
│ ├── IntMinStack.java, MinStack.java, EncodedMinStack.java problem 3
│ ├── MonotonicStack.java problems 4-7
│ ├── QueueViaStacks.java, StackViaQueue.java problems 9, 10
│ ├── BruteForce.java slow, obviously-correct references
│ ├── DryRuns.java instrumented copies that record every step
│ ├── Complexity.java operation counters (counted, not timed)
│ ├── Pitfalls.java plausible-looking wrong versions
│ └── JdkStackDemo.java java.util.Stack versus ArrayDeque
├── src/test/java/.../ SolutionsTest, DryRunTest, RandomAgreementTest, ComplexityTest, PitfallsTest, JdkStackTest
└── output/*.txt captured real output
```