Fayllar bilan bayt-bayt ishlash

Qani boshladik

• Konsoldan fayl nomini kiriting
• Fayldagi barcha baytlarni o'qing.
• Takrorlashlarga e'tibor bermay, ularni bayt-kod bo'yicha kamayish tartibida tartiblang.
• Displey
• I/U oqimini yoping

Keling, buni to'g'ridan-to'g'ri hal qilaylik:

// Вариант 1. Загоняем в коллекцию и сортируем используя ее метод Collections.sort
public class Solution {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());
        long startTime = System.currentTimeMillis();

        ArrayList<Integer> listData = new ArrayList<Integer>();
        while (inputStream.available() > 0) listData.add(inputStream.read());
        inputStream.close();
        ArrayList<Integer> result = new ArrayList<Integer>(new HashSet<Integer>(listData));
        Collections.sort(result);

        while (!result.isEmpty()) {
            System.out.print(result.get(result.size()-1) + " ");
            result.remove(result.get(result.size()-1));
        }

        long finishTime = System.currentTimeMillis();
        System.out.println("\nвремя работы=" + (finishTime-startTime) + "ms.");
    }
}

TreeSet bilan tanishing

• ikkita bir xil elementni saqlashga ruxsat bermaydi (ya'ni biz milliard o'rniga barcha 255 elementni xotirada saqlaymiz!)
• uning elementlarini manipulyatsiya qilganda, u avtomatik ravishda tartibga soladi (o'zini saralaydi - mana bu mukammallik balandligi!)

// Вариант 2. Загоняем в ТreeSet который сам сортирует (лютый win!)
public class Solution {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());

        byte[] arrBytes = new byte[256];
        long startTime = System.currentTimeMillis();

        SortedSet<Integer> list = new TreeSet<Integer>();
        while(inputStream.available()>0) list.add(inputStream.read());
        inputStream.close();

        while (!list.isEmpty())        {
            System.out.print(list.last() + " ");
            list.remove(list.last());
        }

		long finishTime = System.currentTimeMillis();
        System.out.println("\nвремя работы=" + (finishTime-startTime) + "ms.");
    }
}

Massiv - bayt-bayt

// Вариант 3. Считываем массив поbyteно.
public class Solution {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());

        long[] arrBytes = new long[256];
        long startTime = System.currentTimeMillis();

        while (inputStream.available() > 0) arrBytes[inputStream.read()]++;

		inputStream.close();
        // Выводим отсортированный по byte-codeу в обратном порядке
        for (long i = 255; i >= 0 ; i--)
            if (arrBytes[(int) i] > 0) System.out.print(i + " ");

			long finishTime = System.currentTimeMillis();
        System.out.println("\nвремя работы=" + (finishTime-startTime) + "ms.");
    }
}

Keling, birdaniga BUTUN KAMAZni qum bilan to'kib tashlaymiz!

// Вариант 4. Считываем массив сразу целиком за раз в память.
public class Solution {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());

        long[] arrBytes = new long[256];
        long startTime = System.currentTimeMillis();

        byte fileImage[]=new byte[inputStream.available()];
        long fileSize=fileImage.length;
        inputStream.read(fileImage);
        for (int i = 0; i = 0 ; i--)
            if (arrBytes[(int) i] > 0) System.out.print(i + " ");

		long finishTime = System.currentTimeMillis();
        System.out.println("\nвремя работы=" + (finishTime-startTime) + "ms.");
    }
}

1. arrBytes indeksi 0..255 ichida aniqlanadi,
2. fileImage bayt massivi bo'lib, uning elementlari -128..127 qiymatiga ega

Buferdan foydalanish

// Вариант 5. Считываем массив кусками.
public class Solution {
    public static void main(String[] args) throws Exception {
        FileInputStream inputStream = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());

        long[] arrBytes = new long[256];
        long startTime = System.currentTimeMillis();

        int  bufferSize = 64000;
        byte buffer[]   = new byte[64000];

        while (inputStream.available() > 0) {
            if (inputStream.available() < 64000) bufferSize = inputStream.available();
            inputStream.read(buffer, 0, bufferSize );
            for (int i = 0; i = 0 ; i--)
            if (arrBytes[(int) i] > 0) System.out.print(i + " ");

		long finishTime = System.currentTimeMillis();
        System.out.println("\nвремя работы=" + (finishTime-startTime) + "ms.");
    }
}