SPA ORCA Technical Screen & Whiteboard Cheatsheet

1. Strategy for Hiring Team (Engineering Leads & OR Analysts)

2. C# to Java Translation Cheatsheet (Your Rapid Reference)

You have strong C# intuition. Java is 90% identical, but small syntax differences will trip you up on a whiteboard. Use this exact comparison table:

3. The 5-Step Incomplete-Problem Whiteboard Execution Framework

SPA interviewers typically give you an incomplete class hierarchy or a buggy method and ask: "Complete this method so our radar tracker correctly handles this scenario." Follow this exact 5-step framework:

// Clean structure
public void ingest(Track track) {
    if (!isValid(track)) return; // Guard clause
    activeTracks.put(track.getTrackId(), track); // Upsert
}

4. The 3 SPA Defense Modeling Problem Archetypes

Archetype A: PriorityQueue Threat Allocator (Min-Heap by TTI)

The Problem: DDG-79 has 15 hostile contacts. You must allocate weapons to the most urgent threats first (lowest Time to Impact = highest danger).

// Java Implementation — Target Interview Code
import java.util.*;

public class ThreatEvaluator {

    public List<Track> getHighestPriorityThreats(List<Track> tracks, int k) {
        // 1. Guard against null, empty list, or non-positive k
        if (tracks == null || tracks.isEmpty() || k <= 0) {
            return Collections.emptyList();
        }

        // 2. Min-Heap: smallest TTI comes off first
        PriorityQueue<Track> pq = new PriorityQueue<>(
            (a, b) -> Double.compare(a.getTimeToImpact(), b.getTimeToImpact())
        );

        // 3. Filter: only active, un-neutralized hostiles
        for (Track t : tracks) {
            if (t != null && t.isHostile() && !t.isNeutralized()) {
                pq.offer(t);
            }
        }

        // 4. Extract top-K threats
        List<Track> result = new ArrayList<>();
        while (!pq.isEmpty() && result.size() < k) {
            result.add(pq.poll());
        }

        return result;
    }
}

Archetype B: Track Ingestion & Boundary Filter (Upsert & Validation)

The Problem: Write ingest(Track track) to validate incoming radar tracks against geographic boundaries and store them in the active map.

// Java Implementation
public class TrackManager {
    private final Map<String, Track> activeTracks = new HashMap<>();

    public void ingest(Track track) {
        // 1. Null check guard
        if (track == null) return;

        // 2. Empty ID guard
        if (track.getTrackId() == null || track.getTrackId().trim().isEmpty()) return;

        // 3. Boundary validation
        double lat = track.getLat();
        double lon = track.getLon();
        if (lat < -90.0 || lat > 90.0 || lon < -180.0 || lon > 180.0) return;

        // 4 & 5. Upsert: overwrites existing record if present, inserts if new
        activeTracks.put(track.getTrackId(), track);
    }

    public Map<String, Track> getActiveTracks() {
        return Collections.unmodifiableMap(activeTracks);
    }
}

Archetype C: Extensible Sensor Parser (Factory / Registry Pattern)

The Problem: Replace a fragile if/else-if parser with an extensible design that adheres to the Open/Closed Principle.

// Java Implementation
public interface SensorParser {
    Track parseRecord(byte[] payload);
}

public class SensorIngestionService {
    // Registry of parsers by sensor type
    private final Map<SensorType, SensorParser> parsers = new HashMap<>();
    private final Map<String, Track> activeTracks = new ConcurrentHashMap<>();

    public void registerParser(SensorType type, SensorParser parser) {
        if (type != null && parser != null) {
            parsers.put(type, parser);
        }
    }

    public void ingest(SensorType type, byte[] payload) {
        SensorParser parser = parsers.get(type);
        if (parser == null) {
            throw new IllegalArgumentException("No parser registered for: " + type);
        }

        Track track = parser.parseRecord(payload);
        if (track != null && track.isValid()) {
            activeTracks.put(track.getTrackId(), track);
        }
    }
}

5. Verbatim Speaking Scripts for the Room

6. Defense Domain Primer for Software Engineers