first commit

Author: alansastre

.gitignore

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+
+### Eclipse ###
+.metadata
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/
+.loadpath
+.recommenders
+
+# External tool builders
+.externalToolBuilders/
+
+# Locally stored "Eclipse launch configurations"
+*.launch
+
+# PyDev specific (Python IDE for Eclipse)
+*.pydevproject
+
+# CDT-specific (C/C++ Development Tooling)
+.cproject
+
+# CDT- autotools
+.autotools
+
+# Java annotation processor (APT)
+.factorypath
+
+# PDT-specific (PHP Development Tools)
+.buildpath
+
+# sbteclipse plugin
+.target
+
+# Tern plugin
+.tern-project
+
+# TeXlipse plugin
+.texlipse
+
+# STS (Spring Tool Suite)
+.springBeans
+
+# Code Recommenders
+.recommenders/
+
+# Annotation Processing
+.apt_generated/
+.apt_generated_test/
+
+# Scala IDE specific (Scala & Java development for Eclipse)
+.cache-main
+.scala_dependencies
+.worksheet
+
+# Uncomment this line if you wish to ignore the project description file.
+# Typically, this file would be tracked if it contains build/dependency configurations:
+#.project
+
+### Eclipse Patch ###
+# Spring Boot Tooling
+.sts4-cache/
+
+### Intellij+all ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# AWS User-specific
+.idea/**/aws.xml
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn. Uncomment if using
+# auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+*.iml
+
+# *.ipr
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# IntelliJ
+out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# SonarLint plugin
+.idea/sonarlint/
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Intellij+all Patch ###
+# Ignore everything but code style settings and run configurations
+# that are supposed to be shared within teams.
+
+.idea/*
+
+!.idea/codeStyles
+!.idea/runConfigurations
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+replay_pid*
+
+### Maven ###
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+.mvn/timing.properties
+# https://github.com/takari/maven-wrapper#usage-without-binary-jar
+.mvn/wrapper/maven-wrapper.jar
+
+# Eclipse m2e generated files
+# Eclipse Core
+.project
+# JDT-specific (Eclipse Java Development Tools)
+.classpath
+
+### VisualStudioCode ###
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+!.vscode/*.code-snippets
+
+# Local History for Visual Studio Code
+.history/
+
+# Built Visual Studio Code Extensions
+*.vsix
+
+### VisualStudioCode Patch ###
+# Ignore all local history of files
+.history
+.ionide
+

README.md

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+# Recursión en Java
+
+Resolución de problemas utilizando enfoques:
+
+* Iterativo
+* Recursivo
+* Recursivo de cola

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+
+ <groupId>org.example</groupId>
+ <artifactId>java-recursion</artifactId>
+ <version>1.0-SNAPSHOT</version>
+
+ <properties>
+ <maven.compiler.source>18</maven.compiler.source>
+ <maven.compiler.target>18</maven.compiler.target>
+ </properties>
+
+</project>

src/main/java/com/example/Factorial.java

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+package com.example;
+
+import java.time.Duration;
+import java.time.Instant;
+
+public class Factorial {
+
+ public static void main(String[] args) {
+ Long number = 20L;
+ long start = System.currentTimeMillis();
+ long result = factorialIterative(number);
+ long end = System.currentTimeMillis();
+ System.out.println("Tiempo: " + (end - start) + ", Resultado: " + result);
+
+ number = 20L;
+ start = System.currentTimeMillis();
+ result = factorialRecursive(number);
+ end = System.currentTimeMillis();
+ System.out.println("Tiempo: " + (end - start) + ", Resultado: " + result);
+
+ number = 20L;
+ start = System.currentTimeMillis();
+ result = factorialRecursiveTail(number);
+ end = System.currentTimeMillis();
+ System.out.println("Tiempo: " + (end - start) + ", Resultado: " + result);
+
+ }
+
+ static long factorialIterative(Long num){
+ long result = 1;
+ for(int i = 1; i<=num; i++)
+ result *= i;
+
+ return result;
+ }
+
+ static long factorialRecursive(Long num){
+ if(num == 1)
+ return 1;
+ return num * factorialRecursive(num - 1);
+ }
+
+ // Versión mejorada de la recusión: recursión de cola
+
+ static long factorialRecursiveTail(Long num){
+ return factorialHelper(1, num);
+ }
+
+ static long factorialHelper(long acumulador, Long num){
+ if (num == 1)
+ return acumulador;
+ return factorialHelper(acumulador * num, num - 1);
+ }
+
+}

src/main/java/com/example/Reverse.java

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+package com.example;
+
+public class Reverse {
+
+ public static void main(String[] args) {
+ String text = "ABC";
+
+ String reversed = reverseIterative(text);
+ System.out.println(reversed);
+
+ reversed = reverseRecursive(text);
+ System.out.println(reversed);
+
+ reversed = reverseRecursiveTail(text, "");
+ System.out.println(reversed);
+ }
+
+
+
+
+ private static String reverseIterative(String text) {
+
+ byte[] textBytes = text.getBytes();
+ byte[] result = new byte[textBytes.length];
+
+ for(int i = 0; i < textBytes.length; i++){
+ result[i] = textBytes[textBytes.length - i - 1];
+ }
+
+ return new String(result);
+ }
+
+ /*
+ reverseRecursive("ABC")
+ reverseRecursive("BC") + 'A'
+ (reverseRecursive("C") + 'B') + 'A'
+ ("C" + 'B') + 'A'
+ "CB" + 'A'
+ "CBA"
+
+ */
+ private static String reverseRecursive(String text) {
+ if(text.isEmpty())
+ return text;
+ return reverseRecursive(text.substring(1)) + text.charAt(0);
+ }
+
+ // recursión mejorada
+ /*
+ reverseRecursiveTail("ABC", "")
+ reverseRecursiveTail("BC", "A")
+ reverseRecursiveTail("C", "BA")
+ reverseRecursiveTail("", "CBA")
+ "CBA"
+ */
+ private static String reverseRecursiveTail(String text, String acumulador) {
+ if(text.isEmpty())
+ return acumulador;
+ return reverseRecursiveTail(text.substring(1), text.charAt(0) + acumulador);
+ }
+
+}