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/*
 * Problem: Given a list of paths where each path represents a direct trip from city A to city B, 
 * the goal is to find the final destination city which has no outgoing paths.
 * Approach: Use Java Streams to process the list of paths, extract destination cities, and filter out starting cities.
 */
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

public class DestinationCityStream {
    public String destCity(List<List<String>> paths) {
        // Create a set of destination cities using streams
        Set<String> destinationSet = paths.stream()
            .map(path -> path.get(1))
            .collect(Collectors.toSet());

        // Remove all cities that are starting points of any path
        paths.stream()
            .map(path -> path.get(0))
            .forEach(destinationSet::remove);

        // The remaining city is the final destination
        return destinationSet.iterator().next();
    }
}