Notes

#include <stdio.h>
#include <time.h>

void swap(int* a, int* b)
{
int t = *a;
*a = *b;
*b = t;
}
int partition (int arr[], int low, int high)
{
int pivot = arr[high]; // pivot
int i = (low - 1); // Index of smaller element

for (int j = low; j <= high- 1; j++)
{
// If current element is smaller than the pivot
if (arr[j] < pivot)
{
i++; // increment index of smaller element
swap(&arr[i], &arr[j]);
}
}
swap(&arr[i + 1], &arr[high]);
return (i + 1);
}
void quicksort(int arr[], int low, int high)
{
if (low < high)
{
/* pi is partitioning index, arr[p] is now
at right place */
int pi = partition(arr, low, high);

// Separately sort elements before
// partition and after partition
quicksort(arr, low, pi - 1);
quicksort(arr, pi + 1, high);
}
}

void quicksortrev(int a[],int n)
{
for(int i=0;i<n/2;i++)
{
int p=a[i];
a[i]=a[n-i-1];
a[n-i-1]=p;
}
}
int main()
{


clock_t avg,best,worst;
int arr[10000];
for(int i=0;i<10000;i++)
{

arr[i]=rand()%1000000+1;

}



int n = sizeof(arr)/sizeof(arr[0]);
avg = clock(); // it will store the the current time means time before execution of bubble sort function
quicksort(arr,0,n-1);
avg = clock() - avg; // it will store the the time taken means time after execution of bubble sort function - time before the execution of bubble sort
double time_taken = ((double)avg)/CLOCKS_PER_SEC; // in seconds
printf("average case took %f seconds to execute n", time_taken);

best = clock();
quicksort(arr,0,n-1);
best = clock() - best;
double time_taken2 = ((double)best)/CLOCKS_PER_SEC; // in seconds
printf("best case took %f seconds to execute n", time_taken2);

quicksortrev(arr,n);
worst = clock();
quicksort(arr,0,n-1);
worst = clock() - worst;
double time_taken3 = ((double)worst)/CLOCKS_PER_SEC; // in seconds
printf("worst case took %f seconds to execute n", time_taken3);


return 0;
}