HackerrankPsAlgorithms0081.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

public class HackerrankPsAlgorithms0081 {

	// Gemstones
	// https://www.hackerrank.com/challenges/gem-stones/problem?isFullScreen=true

	static class Result {

		public static int gemstones(List<String> arr) {
			Set<Character> firstStoneSet = new HashSet<>();
			for (char c : arr.get(0).toCharArray()) {
				firstStoneSet.add(c);
			}

			for (int i = 1; i < arr.size(); i++) {
				String stone = arr.get(i);
				Set<Character> currentStoneSet = new HashSet<>();

				for (char c : stone.toCharArray()) {
					currentStoneSet.add(c);
				}

				firstStoneSet.retainAll(currentStoneSet);
			}
			return firstStoneSet.size();
		}

	}

	public static void main(String[] args) throws IOException {
		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

		int n = Integer.parseInt(bufferedReader.readLine().trim());

		List<String> arr = IntStream.range(0, n).mapToObj(i -> {
			try {
				return bufferedReader.readLine();
			} catch (IOException ex) {
				throw new RuntimeException(ex);
			}
		})
				.collect(toList());

		int result = Result.gemstones(arr);

		bufferedWriter.write(String.valueOf(result));
		bufferedWriter.newLine();

		bufferedReader.close();
		bufferedWriter.close();
	}

}