Answers for "the quick sort algorithm selects the first element in the list as the pivot. Revise it by selecting the median among the first, middle, and last elements in the list."

quick sort

//I Love Java
import java.io.*;
import java.util.*;
import java.util.stream.*;
import static java.util.Collections.*;

import static java.util.stream.Collectors.*;

public class Quick_Sort_P {

    static void swap(List<Integer> arr, int i, int j) {
        int temp = arr.get(i);
        arr.set(i, arr.get(j));
        arr.set(j, temp);
    }

    static int partition(List<Integer> arr, int low, int high) {

        int pivot = arr.get(high);
        int i = (low - 1);

        for (int j = low; j <= high - 1; j++) {

            if (arr.get(j) < pivot) {

                i++;
                swap(arr, i, j);
            }
        }
        swap(arr, i + 1, high);
        return (i + 1);
    }

    static void quickSort(List<Integer> arr, int low, int high) {
        if (low < high) {

            int pi = partition(arr, low, high);

            quickSort(arr, low, pi - 1);
            quickSort(arr, pi + 1, high);
        }
    }

    public static void main(String[] args) throws IOException {

        BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));

        List<Integer> arr = Stream.of(buffer.readLine().replaceAll("\\s+$", "").split(" ")).map(Integer::parseInt)
                .collect(toList());

        int n = arr.size();

        quickSort(arr, 0, n - 1);
        System.out.println("Sorted array: ");
        System.out.println(arr);
    }
}

quick sort

//I Love Java
import java.io.*;
import java.util.*;
import java.util.stream.*;
import static java.util.Collections.*;

import static java.util.stream.Collectors.*;

public class Quick_Sort_P {

    static void swap(List<Integer> arr, int i, int j) {
        int temp = arr.get(i);
        arr.set(i, arr.get(j));
        arr.set(j, temp);
    }

    static int partition(List<Integer> arr, int low, int high) {

        int pivot = arr.get(high);
        int i = (low - 1);

        for (int j = low; j <= high - 1; j++) {

            if (arr.get(j) < pivot) {

                i++;
                swap(arr, i, j);
            }
        }
        swap(arr, i + 1, high);
        return (i + 1);
    }

    static void quickSort(List<Integer> arr, int low, int high) {
        if (low < high) {

            int pi = partition(arr, low, high);

            quickSort(arr, low, pi - 1);
            quickSort(arr, pi + 1, high);
        }
    }

    public static void main(String[] args) throws IOException {

        BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));

        List<Integer> arr = Stream.of(buffer.readLine().replaceAll("\\s+$", "").split(" ")).map(Integer::parseInt)
                .collect(toList());

        int n = arr.size();

        quickSort(arr, 0, n - 1);
        System.out.println("Sorted array: ");
        System.out.println(arr);
    }
}