Question

3. Write a computer program that prompts the user for one number, n for the number of items in the array to sort, and create and sort 1000 different arrays of this size timing the run to get an average time to sort an array of this size. Then do the following:

   Initiate a variable running_time to 0

   Create a for loop that iterates 1000 times.

   In the body of the loop,

   Create an array of n random integers (Make sure you make the range of the random numbers substantially bigger than the array, ie. if the array size is 500 have the random number generator pick numbers between 1 and 5000. For the largest array have the random number generator pick numbers between 1 and 50,000).

   Get the time and set this to start-time (notice the sort is started after each array is built. You want to time the srt process only). You will have to figure out what the appropriate command is in the programming language you are using to find the time (Important: Do not start the timer until after the array is created).

   Use bubble sort to sort the array

   Get the time and set this to end-time Subtract start-time from end-time and add the result to total_time

   Once the program has run, note

   The number of items sorted

   The average running time for each array (total_time/1000)

   Repeat the process using 500, 2500 and 5000 as the size of the array.

4. Repeat 3 using selection sort.

Answer 1

import java.util.*;
public class CalculateSortTime{
public static void main(String [] args){
  
Scanner sc=new Scanner(System.in);
System.out.print("The arr of items in the array to sort :");
int noOfItems = sc.nextInt();
printTimeBubbleSort(noOfItems);
printTimeSelctionSort(noOfItems);
}
public static void printTimeBubbleSort(int noOfItems){
   Random random = new Random();
   long totalTime = 0;
for(int i=0;i<1000;i++){
int [] arr = new int [noOfItems];
for (int d = 0 ; d<arr.length ; d++)
{
int randomNumber = random.nextInt(noOfItems*10)+1;
arr[d] = randomNumber;
}
long startTime = System.currentTimeMillis();
arr = BubbleSort(arr);
long stopTime = System.currentTimeMillis();
long elapsedTime = stopTime - startTime;
totalTime+=elapsedTime;
}
System.out.println("Using BubbleSort The average running time for each array with size "+noOfItems+" is "+totalTime/1000.0+" sec");
}
public static void printTimeSelctionSort(int noOfItems){
   Random random = new Random();
   long totalTime = 0;
for(int i=0;i<1000;i++){
int [] arr = new int [noOfItems];
for (int d = 0 ; d<arr.length ; d++)
{
int randomNumber = random.nextInt(noOfItems*10)+1;
arr[d] = randomNumber;
}
long startTime = System.currentTimeMillis();
arr = SelectionSort(arr);
long stopTime = System.currentTimeMillis();
long elapsedTime = stopTime - startTime;
totalTime+=elapsedTime;
}
System.out.println("Using Selection Sort The average running time for each array with size "+noOfItems+" is "+totalTime/1000.0+" sec");
}
public static int [] BubbleSort(int[] array)
{
int temp;
for(int i = 0 ; i < array.length-1 ; i++){
for ( int j = 0 ; j < array.length-i-1 ; j++){
   //sorting
if ( array[j] > array[j+1]){
temp = array[j];
array[j] = array[j+1];
array[j+1] = temp;
}

}
}
return array;   
}
public static int [] SelectionSort(int[] arr)
{
int n = arr.length;
for (int i = 0; i < n-1; i++)
{
int min_idx = i;
for (int j = i+1; j < n; j++)
if (arr[j] < arr[min_idx])
min_idx = j;
int temp = arr[min_idx];
arr[min_idx] = arr[i];
arr[i] = temp;
}
       return arr;
}
}