Question

In java create a program to test and measure an actual running time of Insertion sort and Merge sort on your machine. Each sorting algorithm must be a separate method:

a. Randomly generate 100 integers between 0 and 500.

b. Store those integers in an array and display them on screen.

c. Using each sorting algorithm, sort numbers and display the sorted numbers. The array must be passed as an argument to call a method.

d. For each sorting algorithm, measure an actual running time (millisecond or nanosecond) taken in sorting numbers on your machine and save the time in a temporary variable(s) or an array. The actual running time would be the elapsed time from start to end of sorting.

e. Repeat a – d five times at least.

f. Display five running times measured for both sorting algorithms.

g. Calculate an average of the five running times for both and display them. h. All data display must appear in a tabular format.

Answer 1

You may wanna change time from milli seconds to nano seconds in case it is displaying all zeros.
The code is self explanatory. Follow up in comments if there are any doubts.

import java.util.*;

public class Sort{

private static int rand(int min, int max) {
Random r = new Random();
return r.nextInt((max - min) + 1) + min;
}

void insertionSort(int arr[]) {
int n = arr.length;
for (int i=1; i<n; ++i){
int key = arr[i];
int j = i-1;
while (j>=0 && arr[j] > key){
arr[j+1] = arr[j];
j = j-1;
}
arr[j+1] = key;
}
}
  
void mergeSort(int arr[], int l, int r){
if (l < r) {
int m = (l+r)/2;
mergeSort(arr, l, m);
mergeSort(arr , m+1, r);
merge(arr, l, m, r);
}
}
  
void merge(int arr[], int l, int m, int r)
{
int n1 = m - l + 1;
int n2 = r - m;
int L[] = new int [n1];
int R[] = new int [n2];
  
for (int i=0; i<n1; ++i) L[i] = arr[l + i];
for (int j=0; j<n2; ++j) R[j] = arr[m + 1+ j];
  
int i = 0, j = 0;
int k = l;
while (i < n1 && j < n2){
if (L[i] <= R[j]) arr[k++] = L[i++];
else arr[k++] = R[j++];
}
while (i < n1) arr[k++] = L[i++];
while (j < n2) arr[k++] = R[j++];
}

public static void main(String[] args) {
Sort obj = new Sort();
int[] arr = new int[100];
long en, insAvg=0, merAvg=0;

for(int i=0;i<5;i++){
for(int i=0;i<arr.size;i++){
arr[i] = rand(0, 500+1);
System.out.print(arr[i]+" ");
}
int[] copy = Arrays.copyOf(arr, arr.length);
long st = System.currentTimeMillis();
insertionSort(copy);
en = System.currentTimeMillis() - st;
System.out.println((i+1) + ". Time taken by Insertion Sort: " + en);
insAvg += en;

int[] copy = Arrays.copyOf(arr, arr.length);
long st = System.currentTimeMillis();
mergeSort(copy, 0, copy.length-1);
en = System.currentTimeMillis() - st;
System.out.println((i+1) + ". Time taken by Merge Sort: " + en);
insAvg += en;
}
  
System.out.println("Average Time taken by insertion sort: " + insAvg/5.0);
System.out.println("Average Time taken by merge sort: " + merAvg/5.0);

}

}