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DenizAltunkapanDenizAltunkapan
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Merge branch 'master' into feat-hierholzer-algorithm
2 parents a62a7c4 + 0837424 commit 78d950c

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‎.github/workflows/close-failed-prs.yml‎

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name: Close stale PRs with failed workflows
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on:
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schedule:
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- cron: '0 3 * * *' # runs daily at 03:00 UTC
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workflow_dispatch:
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permissions:
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contents: read
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issues: write
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pull-requests: write
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jobs:
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close-stale:
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runs-on: ubuntu-latest
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steps:
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- name: Close stale PRs
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uses: actions/github-script@v8
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with:
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github-token: ${{ secrets.GITHUB_TOKEN }}
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script: |
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const mainBranches = ['main', 'master'];
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const cutoffDays = 14;
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const cutoff = new Date();
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cutoff.setDate(cutoff.getDate() - cutoffDays);
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console.log(`Checking PRs older than: ${cutoff.toISOString()}`);
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try {
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const { data: prs } = await github.rest.pulls.list({
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owner: context.repo.owner,
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repo: context.repo.repo,
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state: 'open',
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sort: 'updated',
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direction: 'asc',
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per_page: 100
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});
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console.log(`Found ${prs.length} open PRs to check`);
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for (const pr of prs) {
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try {
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const updated = new Date(pr.updated_at);
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if (updated > cutoff) {
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console.log(`⏩ Skipping PR #${pr.number} - updated recently`);
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continue;
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}
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console.log(`🔍 Checking PR #${pr.number}: "${pr.title}"`);
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// Get commits
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const commits = await github.paginate(github.rest.pulls.listCommits, {
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owner: context.repo.owner,
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repo: context.repo.repo,
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pull_number: pr.number,
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per_page: 100
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});
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const meaningfulCommits = commits.filter(c => {
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const msg = c.commit.message.toLowerCase();
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const isMergeFromMain = mainBranches.some(branch =>
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msg.startsWith(`merge branch '${branch}'`) ||
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msg.includes(`merge remote-tracking branch '${branch}'`)
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);
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return !isMergeFromMain;
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});
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// Get checks with error handling
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let hasFailedChecks = false;
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let allChecksCompleted = false;
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let hasChecks = false;
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try {
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const { data: checks } = await github.rest.checks.listForRef({
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owner: context.repo.owner,
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repo: context.repo.repo,
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ref: pr.head.sha
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});
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hasChecks = checks.check_runs.length > 0;
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hasFailedChecks = checks.check_runs.some(c => c.conclusion === 'failure');
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allChecksCompleted = checks.check_runs.every(c =>
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c.status === 'completed' || c.status === 'skipped'
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);
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} catch (error) {
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console.log(`⚠️ Could not fetch checks for PR #${pr.number}: ${error.message}`);
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}
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// Get workflow runs with error handling
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let hasFailedWorkflows = false;
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let allWorkflowsCompleted = false;
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let hasWorkflows = false;
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try {
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const { data: runs } = await github.rest.actions.listWorkflowRuns({
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owner: context.repo.owner,
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repo: context.repo.repo,
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head_sha: pr.head.sha,
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per_page: 50
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});
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hasWorkflows = runs.workflow_runs.length > 0;
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hasFailedWorkflows = runs.workflow_runs.some(r => r.conclusion === 'failure');
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allWorkflowsCompleted = runs.workflow_runs.every(r =>
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['completed', 'skipped', 'cancelled'].includes(r.status)
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);
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console.log(`PR #${pr.number}: ${runs.workflow_runs.length} workflow runs found`);
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} catch (error) {
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console.log(`⚠️ Could not fetch workflow runs for PR #${pr.number}: ${error.message}`);
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}
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console.log(`PR #${pr.number}: ${meaningfulCommits.length} meaningful commits`);
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console.log(`Checks - has: ${hasChecks}, failed: ${hasFailedChecks}, completed: ${allChecksCompleted}`);
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console.log(`Workflows - has: ${hasWorkflows}, failed: ${hasFailedWorkflows}, completed: ${allWorkflowsCompleted}`);
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// Combine conditions - only consider if we actually have checks/workflows
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const hasAnyFailure = (hasChecks && hasFailedChecks) || (hasWorkflows && hasFailedWorkflows);
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const allCompleted = (!hasChecks || allChecksCompleted) && (!hasWorkflows || allWorkflowsCompleted);
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if (meaningfulCommits.length === 0 && hasAnyFailure && allCompleted) {
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console.log(`✅ Closing PR #${pr.number} (${pr.title})`);
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await github.rest.issues.createComment({
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owner: context.repo.owner,
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repo: context.repo.repo,
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issue_number: pr.number,
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body: `This pull request has been automatically closed because its workflows or checks failed and it has been inactive for more than ${cutoffDays} days. Please fix the workflows and reopen if you'd like to continue. Merging from main/master alone does not count as activity.`
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});
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await github.rest.pulls.update({
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owner: context.repo.owner,
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repo: context.repo.repo,
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pull_number: pr.number,
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state: 'closed'
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});
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console.log(`✅ Successfully closed PR #${pr.number}`);
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} else {
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console.log(`⏩ Not closing PR #${pr.number} - conditions not met`);
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}
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} catch (prError) {
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console.error(`❌ Error processing PR #${pr.number}: ${prError.message}`);
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continue;
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}
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}
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} catch (error) {
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console.error(`❌ Fatal error: ${error.message}`);
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throw error;
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}

‎pom.xml‎

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<dependency>
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<groupId>org.junit</groupId>
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<artifactId>junit-bom</artifactId>
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<version>6.0.0</version>
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<version>6.0.1</version>
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<type>pom</type>
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<scope>import</scope>
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</dependency>
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<dependency>
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<groupId>com.puppycrawl.tools</groupId>
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<artifactId>checkstyle</artifactId>
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<version>12.0.1</version>
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<version>12.1.1</version>
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</dependency>
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</dependencies>
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</plugin>
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<plugin>
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<groupId>com.github.spotbugs</groupId>
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<artifactId>spotbugs-maven-plugin</artifactId>
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<version>4.9.7.0</version>
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<version>4.9.8.1</version>
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<configuration>
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<excludeFilterFile>spotbugs-exclude.xml</excludeFilterFile>
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<includeTests>true</includeTests>

‎src/main/java/com/thealgorithms/compression/ArithmeticCoding.java‎

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package com.thealgorithms.compression;
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import java.math.BigDecimal;
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import java.math.MathContext;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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/**
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* An implementation of the Arithmetic Coding algorithm.
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*
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* <p>
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* Arithmetic coding is a form of entropy encoding used in lossless data
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* compression. It encodes an entire message into a single number, a fraction n
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* where (0.0 <= n < 1.0). Unlike Huffman coding, which assigns a specific
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* bit sequence to each symbol, arithmetic coding represents the message as a
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* sub-interval of the [0, 1) interval.
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* </p>
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*
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* <p>
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* This implementation uses BigDecimal for precision to handle the shrinking
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* intervals, making it suitable for educational purposes to demonstrate the
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* core logic.
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* </p>
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*
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* <p>
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* Time Complexity: O(n*m) for compression and decompression where n is the
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* length of the input and m is the number of unique symbols, due to the need
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* to calculate symbol probabilities.
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* </p>
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*
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* <p>
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* References:
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* <ul>
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* <li><a href="https://en.wikipedia.org/wiki/Arithmetic_coding">Wikipedia:
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* Arithmetic coding</a></li>
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* </ul>
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* </p>
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*/
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public final class ArithmeticCoding {
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private ArithmeticCoding() {
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}
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/**
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* Compresses a string using the Arithmetic Coding algorithm.
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*
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* @param uncompressed The string to be compressed.
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* @return The compressed representation as a BigDecimal number.
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* @throws IllegalArgumentException if the input string is null or empty.
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*/
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public static BigDecimal compress(String uncompressed) {
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if (uncompressed == null || uncompressed.isEmpty()) {
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throw new IllegalArgumentException("Input string cannot be null or empty.");
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}
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Map<Character, Symbol> probabilityTable = calculateProbabilities(uncompressed);
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BigDecimal low = BigDecimal.ZERO;
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BigDecimal high = BigDecimal.ONE;
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for (char symbol : uncompressed.toCharArray()) {
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BigDecimal range = high.subtract(low);
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Symbol sym = probabilityTable.get(symbol);
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high = low.add(range.multiply(sym.high()));
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low = low.add(range.multiply(sym.low()));
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}
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return low; // Return the lower bound of the final interval
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}
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/**
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* Decompresses a BigDecimal number back into the original string.
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*
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* @param compressed The compressed BigDecimal number.
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* @param length The length of the original uncompressed string.
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* @param probabilityTable The probability table used during compression.
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* @return The original, uncompressed string.
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*/
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public static String decompress(BigDecimal compressed, int length, Map<Character, Symbol> probabilityTable) {
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StringBuilder decompressed = new StringBuilder();
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// Create a sorted list of symbols for deterministic decompression, matching the
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// order used in calculateProbabilities
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List<Map.Entry<Character, Symbol>> sortedSymbols = new ArrayList<>(probabilityTable.entrySet());
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sortedSymbols.sort(Map.Entry.comparingByKey());
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BigDecimal low = BigDecimal.ZERO;
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BigDecimal high = BigDecimal.ONE;
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for (int i = 0; i < length; i++) {
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BigDecimal range = high.subtract(low);
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// Find which symbol the compressed value falls into
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for (Map.Entry<Character, Symbol> entry : sortedSymbols) {
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Symbol sym = entry.getValue();
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// Calculate the actual range for this symbol in the current interval
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BigDecimal symLow = low.add(range.multiply(sym.low()));
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BigDecimal symHigh = low.add(range.multiply(sym.high()));
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// Check if the compressed value falls within this symbol's range
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if (compressed.compareTo(symLow) >= 0 && compressed.compareTo(symHigh) < 0) {
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decompressed.append(entry.getKey());
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// Update the interval for the next iteration
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low = symLow;
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high = symHigh;
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break;
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}
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}
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}
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return decompressed.toString();
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}
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/**
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* Calculates the frequency and probability range for each character in the
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* input string in a deterministic order.
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*
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* @param text The input string.
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* @return A map from each character to a Symbol object containing its
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* probability range.
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*/
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public static Map<Character, Symbol> calculateProbabilities(String text) {
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Map<Character, Integer> frequencies = new HashMap<>();
130+
for (char c : text.toCharArray()) {
131+
frequencies.put(c, frequencies.getOrDefault(c, 0) + 1);
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}
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// Sort the characters to ensure a deterministic order for the probability table
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List<Character> sortedKeys = new ArrayList<>(frequencies.keySet());
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Collections.sort(sortedKeys);
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Map<Character, Symbol> probabilityTable = new HashMap<>();
139+
BigDecimal currentLow = BigDecimal.ZERO;
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int total = text.length();
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for (char symbol : sortedKeys) {
143+
BigDecimal probability = BigDecimal.valueOf(frequencies.get(symbol)).divide(BigDecimal.valueOf(total), MathContext.DECIMAL128);
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BigDecimal high = currentLow.add(probability);
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probabilityTable.put(symbol, new Symbol(currentLow, high));
146+
currentLow = high;
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}
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return probabilityTable;
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}
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/**
153+
* Helper class to store the probability range [low, high) for a symbol.
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*/
155+
public record Symbol(BigDecimal low, BigDecimal high) {
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}
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}

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