implementation of Attila Palfi

.gitignore

@@ -0,0 +1,37 @@
+HELP.md
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/

Makefile

@@ -0,0 +1,19 @@
+build-docker:
+	docker build -f distribution/docker/Dockerfile --build-arg JAR_FILE=build/libs/\*.jar -t lindar/bingoticketgenerator-apalfi:0.0.1-SNAPSHOT .
+
+build-gradle:
+	./gradlew clean build
+
+build: build-gradle build-docker
+
+run-docker:
+	docker run -p 8080:8080 lindar/bingoticketgenerator-apalfi:0.0.1-SNAPSHOT
+
+boot-run:
+	./gradlew bootRun
+
+run-tests:
+	./gradlew test --tests "com.attilapalfi.lindar.bingoticketgenerator.ticketgenerator*"
+
+run-perf-tests:
+	./gradlew test --tests 'com.attilapalfi.lindar.bingoticketgenerator.performancetest*'

README.md

@@ -1,3 +1,56 @@
+
+## System Requirements
+- Java 17, gradle
+- Docker
+
+## Build & Run
+Use the Makefile to execute build & run commands.
+
+To build with gradle and docker:
+```shell
+make build
+```
+
+To run the docker container:
+```shell
+make run-docker
+```
+If the container started, the ticket generator endpoint is available at:
+
+### [http://localhost:8080/bingo/newStrips](http://localhost:8080/bingo/newStrips)
+
+To run tests or performance tests:
+```shell
+make run-tests
+make run-perf-tests
+```
+
+## Implementation Details
+- `-1` means `Blank` space in the ticket
+- the core part of the algorithm is in `AbstractTicketGenerator`
+  - it iterates through the spaces of the tickets row by row and based on a set of rules it places the blanks and numbers
+- time complexity of the algorithm is `O(n)` with some amortized time, where `n` is the total number of spaces in the 6 tickets
+  - the algorithm is hard to scale though. it was specifically implemented to generate 3x9 tickets in batches of 6
+- array lists are initialized in the `ArrayBasedTicketGenerator` to keep track of the state of the ticket generator
+  - these array lists are maybe not optimal: removing an element has `O(n)` time complexity
+  - it is possible to create another subclass for `AbstractTicketGenerator` which uses another approach
+    - e.g. instead of array lists, shuffled linked lists. removing from LL: `O(1)`, shuffling during init: `O(nlogn)`
+  - altough these are very small array lists: `n` is usually smaller than 20
+- an error checking is part of the algorithm, because in very rare cases an invalid ticket is generated. 
+As soon as it's detected, the algorithm drops it and starts creating a new one. 
+  - luckily this does not have a performance impact because it's so rare
+
+## Performance
+On my machine the performance test executed with these results:
+
+`Generated 10.000 strips in 487 ms.`
+
+And with 16 threads:
+
+`Generated 100.000 strips in parallel in 1602 ms.`
+
+------
+Original content:
 # Ticket Generator Challenge
 
 A small challenge that involves building a [Bingo 90](https://en.wikipedia.org/wiki/Bingo_(United_Kingdom)) ticket generator.
@@ -19,3 +72,4 @@ A small challenge that involves building a [Bingo 90](https://en.wikipedia.org/w
 
 Try to also think about the performance aspects of your solution. How long does it take to generate 10k strips? 
 The recommended time is less than 1s (with a lightweight random implementation)
+

build.gradle.kts

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+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+	id("org.springframework.boot") version "2.7.1"
+	id("io.spring.dependency-management") version "1.0.11.RELEASE"
+	kotlin("jvm") version "1.6.21"
+	kotlin("plugin.spring") version "1.6.21"
+}
+
+group = "com.attilapalfi.lindar"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_17
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
+	implementation("org.jetbrains.kotlin:kotlin-reflect")
+	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+	kotlinOptions {
+		freeCompilerArgs = listOf("-Xjsr305=strict")
+		jvmTarget = "17"
+	}
+}
+
+tasks.withType<Test> {
+	useJUnitPlatform()
+}

distribution/docker/Dockerfile

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+FROM openjdk:17-alpine
+ARG JAR_FILE=target/*.jar
+COPY ${JAR_FILE} app.jar
+ENTRYPOINT ["java","-jar","/app.jar"]

gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists