4) Write a computer program that prompts the user for one number, n for the numb
ID: 3701235 • Letter: 4
Question
4) 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 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
-Get the time and set this to start-time. 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 selection 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 six times, using 500, 2500 and 5000 as the size of the array for each of the two algorithms.
This is the selection sort program I have for it:
import java.util.Random;
import java.util.Scanner;
class SelectSort {
public static void main(String args[]){
Scanner sc = new Scanner(System.in);
System.out.println("Enter number: ");
int n = sc.nextInt();
int[] arr = new int[n];
Random r = new Random();
//filling random numbers
for(int i=0;i
arr[i] = r.nextInt(100);
}
//printing data
System.out.println("Before selection sort");
for(int i=0;i
System.out.print(arr[i]+" ");
}
System.out.println(" After sorting using selection sort: ");
int temp,j;
for (int i = 1; i < n; i++){
temp = arr[i];
j = i-1;
while (j >= 0 && arr[j] > temp){
arr[j+1] = arr[j];
j = j-1;
}
arr[j+1] = temp;
}
//after selection sort
for(int i=0;i
System.out.print(arr[i]+" ");
}
}
}
Explanation / Answer
import java.util.*;
class SelectionSort
{
public static void selection_sort(int[] a)
{
int i, j, min, x;
// traverse the array
for (i = 0; i < a.length - 1; i++)
{
// store the index of the smallest element
min = i;
// traverse the array from the element after i till the end
for (j = i + 1; j < a.length; j++)
{
// if the current element is smaller than the min element
if (a[j] < a[min])
min = j;
}
// Swap first element and min
x = a[min];
a[min] = a[i];
a[i] = x;
}
}
public static void display(int a[])
{
int n = a.length;
for (int i=0; i<n; ++i)
System.out.print(a[i] + " ");
System.out.println();
}
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
int k;
long total_time = 0;
System.out.print("Enter the size of array : ");
int maxSize = sc.nextInt();
for( k = 1 ; k <= 1000 ; k++ )
{
// initialize the array
int[] a = new int[maxSize];
// fill the array with random elements
for(int j = 0; j < maxSize; j++)
{
int n = (int)( java.lang.Math.random()*(maxSize-1) );
a[j] = n;
}
int i = 0, j = 0;
long x;
//printing data
System.out.println("Before Bubble sort");
display(a);
// get the current time
long start = System.currentTimeMillis();
// sort using bubble sort
selection_sort(a);
// get the current time
long end = System.currentTimeMillis();
// calculate time taken to sort
long time_taken = end - start;
System.out.println("Before Bubble sort");
display(a);
total_time += time_taken;
//System.out.println("Time Taken : " + time_taken);
//display(a);
}
System.out.println(" Average Time : " + ( total_time / 1000.0 ) );
}
}
// output is too long to be included in the solution.
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