Modify the code In the sorting phase use replacement selection and for the merge phase use two-way merge Print content of each generated sorted file as well as the final sorted file using formatted (%6d ) and 10 integers per line.

import java.io.BufferedReader; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.io.PrintWriter; import java.util.Arrays; import java.util.Random; public class Exsort { static int N = 2000000; // ------------- size of the file in disk static int M = 100000; // ----------------- max items the memory buffer can hold public static void extsort(String fileName) { String tfile = "temp-file-"; int[] buffer = new int[M < N ? M : N]; try { FileReader fr = new FileReader(fileName); BufferedReader br = new BufferedReader(fr); int slices = (int) Math.ceil((double) N/M); int i, j; i = j = 0; // Iterate through the elements in the file for (i = 0; i < slices; i++) { // Read M-element chunk at a time from the file for (j = 0; j < (M < N ? M : N); j++) { String t = br.readLine(); if (t != null) buffer[j] = Integer.parseInt(t); else break; } // Sort M elements Arrays.sort(buffer); // Write the sorted numbers to temp file FileWriter fw = new FileWriter(tfile + Integer.toString(i) + ".txt"); PrintWriter pw = new PrintWriter(fw); for (int k = 0; k < j; k++) pw.println(buffer[k]); pw.close(); fw.close(); } br.close(); fr.close(); // Now open each file and merge them, then write back to disk int[] topNums = new int[slices]; BufferedReader[] brs = new BufferedReader[slices]; for (i = 0; i < slices; i++) { brs[i] = new BufferedReader(new FileReader(tfile + Integer.toString(i) + ".txt")); String t = brs[i].readLine(); if (t != null) topNums[i] = Integer.parseInt(t); else topNums[i] = Integer.MAX_VALUE; } FileWriter fw = new FileWriter("E:\\test\\external-sorted.txt"); PrintWriter pw = new PrintWriter(fw); for (i = 0; i < N; i++) { int min = topNums[0]; int minFile = 0; for (j = 0; j < slices; j++) { if (min > topNums[j]) { min = topNums[j]; minFile = j; } } pw.println(min); String t = brs[minFile].readLine(); if (t != null) topNums[minFile] = Integer.parseInt(t); else topNums[minFile] = Integer.MAX_VALUE; } for (i = 0; i < slices; i++) brs[i].close(); pw.close(); fw.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } static String generateInput(int n) { String fileName = "external-sort.txt"; Random rand = new Random(); try { FileWriter fw = new FileWriter(fileName); PrintWriter pw = new PrintWriter(fw); for (int i = 0; i < n; i++) pw.println(rand.nextInt(101)); pw.close(); } catch (IOException e) { e.printStackTrace(); } return fileName; }

public static void main(String[] args)

{

String fileName = generateInput(N);

extsort(fileName);

}

}