Solution1.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

// --- Day 4: Passport Processing ---
// You arrive at the airport only to realize that you grabbed your North Pole
// Credentials instead of your passport. While these documents are extremely
// similar, North Pole Credentials aren't issued by a country and therefore
// aren't actually valid documentation for travel in most of the world.

// It seems like you're not the only one having problems, though; a very long
// line has formed for the automatic passport scanners, and the delay could
// upset your travel itinerary.

// Due to some questionable network security, you realize you might be able to
// solve both of these problems at the same time.

// The automatic passport scanners are slow because they're having trouble
// detecting which passports have all required fields. The expected fields are
// as follows:

// byr (Birth Year)
// iyr (Issue Year)
// eyr (Expiration Year)
// hgt (Height)
// hcl (Hair Color)
// ecl (Eye Color)
// pid (Passport ID)
// cid (Country ID)
// Passport data is validated in batch files (your puzzle input). Each passport
// is represented as a sequence of key:value pairs separated by spaces or
// newlines. Passports are separated by blank lines.

// Here is an example batch file containing four passports:

// ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
// byr:1937 iyr:2017 cid:147 hgt:183cm

// iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
// hcl:#cfa07d byr:1929

// hcl:#ae17e1 iyr:2013
// eyr:2024
// ecl:brn pid:760753108 byr:1931
// hgt:179cm

// hcl:#cfa07d eyr:2025 pid:166559648
// iyr:2011 ecl:brn hgt:59in
// The first passport is valid - all eight fields are present. The second
// passport is invalid - it is missing hgt (the Height field).

// The third passport is interesting; the only missing field is cid, so it looks
// like data from North Pole Credentials, not a passport at all! Surely, nobody
// would mind if you made the system temporarily ignore missing cid fields.
// Treat this "passport" as valid.

// The fourth passport is missing two fields, cid and byr. Missing cid is fine,
// but missing any other field is not, so this passport is invalid.

// According to the above rules, your improved system would report 2 valid
// passports.

// Count the number of valid passports - those that have all required fields.
// Treat cid as optional. In your batch file, how many passports are valid?

public class Solution1 {
    public static void main(String[] args) {
        List<List<String>> input = getInput();
        System.out.println(countValid(input));
    }

    private static List<List<String>> getInput() {
        List<String> fields = new ArrayList<>();
        List<List<String>> input = new ArrayList<>();
        try (BufferedReader br = new BufferedReader(new FileReader("input.txt"))) {
            br.lines().forEach(line -> {
                if (!line.isEmpty())
                    fields.addAll(Arrays.asList(line.trim().split("[ ]+"))); // populate fields with values
                else {
                    input.add(new ArrayList<>(fields)); // add those fields to the input if the line is empty
                    fields.clear();
                }
            });
            if (!fields.isEmpty()) // check if there were values left after EOF
                input.add(fields);
        } catch (Exception e) {
            System.out.println(e);
        }
        return input;
    }

    private static int countValid(List<List<String>> input) {
        int validPassports = 0;
        for (List<String> fields : input) {
            if (fields.size() >= 7)
                if (checkValid(fields))
                    validPassports++;
        }
        return validPassports;
    }

    private static boolean checkValid(List<String> fields) {
        final List<String> validValues = Arrays.asList("pid:", "ecl:", "eyr:", "iyr:", "hgt:", "hcl:", "byr:");
        boolean control;
        for (String param : validValues) {
            control = false;
            for (String field : fields) {
                if (field.contains(param)) {
                    control = true;
                    break;
                }
            }
            if (!control)
                return false;
        }
        return true;
    }
}