Merge Intervals Java Project

This project demonstrates advanced interval algorithms and data structures in Java, using a spec-driven workflow powered by OpenSpec.

Features

1. Interval List Intersections

• Problem: Given two lists of closed, sorted, non-overlapping intervals, compute all their intersections.
• Solution: Implements a two-pointer O(m+n) algorithm in IntervalListIntersections.java.
• Tested in: IntervalListIntersectionsTest.java
• OpenSpec Artifacts:
  • Proposal
  • Design
  • Specs
  • Tasks

2. Count Integers in Intervals

• Problem: Design a data structure to add intervals and count the number of distinct integers covered.
• Solution: Implements a dynamic merge-intervals pattern using a TreeMap in CountIntervals.java for O(log n) add and O(1) count.
• Tested in: CountIntervalsTest.java
• OpenSpec Artifacts:
  • Proposal
  • Design
  • Specs
  • Tasks

How to Run

• Requires Java 17+ and Maven.
• Run all tests:

  mvn test

Project Structure

• src/main/java/org/example/IntervalListIntersections.java — Static interval intersection algorithm
• src/main/java/org/example/CountIntervals.java — Dynamic interval set with add/count
• src/test/java/org/example/IntervalListIntersectionsTest.java — Unit tests for intersections
• src/test/java/org/example/CountIntervalsTest.java — Unit tests for dynamic interval set
• openspec/changes/archive/2026-04-18-interval-list-intersections/ — All OpenSpec artifacts for intersections
• openspec/changes/archive/2026-04-18-count-integers-in-intervals/ — All OpenSpec artifacts for dynamic interval set

About OpenSpec

OpenSpec enables spec-driven development: every change is tracked from proposal to design, specs, tasks, and implementation, with full traceability and testability.