78 lines
1.5 KiB
C++
78 lines
1.5 KiB
C++
/* qsort.cpp
|
|
* Date: 2024-06-22
|
|
* Author: Aryadev Chavali
|
|
* Commentary: The inplace O(nlog(n)) sortitng algorithm. Originally designed
|
|
* in C, hence the lack of iostream.
|
|
*/
|
|
#include <cstdio>
|
|
#include <cstdlib>
|
|
|
|
#define ARR_SIZE(XS) (sizeof(XS) / sizeof((XS)[0]))
|
|
#define SWAP(A, B) \
|
|
do \
|
|
{ \
|
|
(A) ^= (B); \
|
|
(B) ^= (A); \
|
|
(A) ^= (B); \
|
|
} while (0)
|
|
|
|
void print_arr(int *arr, int size)
|
|
{
|
|
printf("{\n");
|
|
for (int i = 0; i < size; ++i)
|
|
printf(" %d,\n", arr[i]);
|
|
printf("}\n");
|
|
}
|
|
|
|
void quicksort(int *arr, int arr_size)
|
|
{
|
|
// TODO: Use a different sort for small enough sizes?
|
|
if (arr_size > 1)
|
|
{
|
|
// TODO: Choose a better pivot maybe?
|
|
int pivot = arr[arr_size - 1]; // Choose the last element as pivot
|
|
int pivot_index = -1;
|
|
|
|
for (int j = 0; j < arr_size; ++j)
|
|
{
|
|
if (arr[j] < pivot)
|
|
{
|
|
++pivot_index;
|
|
std::swap(arr[pivot_index], arr[j]);
|
|
}
|
|
}
|
|
|
|
std::swap(arr[pivot_index + 1], arr[arr_size - 1]);
|
|
|
|
// TODO: Use a stack here instead?
|
|
quicksort(arr, pivot_index + 1);
|
|
quicksort(arr + pivot_index + 1, arr_size - pivot_index - 1);
|
|
}
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
// randomly generate some numbers
|
|
|
|
int *arr = new int[TEST_SIZE];
|
|
|
|
for (size_t i = 0; i < TEST_SIZE; ++i)
|
|
{
|
|
arr[i] = rand() % (2L << 30);
|
|
}
|
|
|
|
printf("Before: ");
|
|
print_arr(arr, TEST_SIZE);
|
|
printf("\n");
|
|
|
|
quicksort(arr, TEST_SIZE);
|
|
|
|
printf("After: ");
|
|
print_arr(arr, TEST_SIZE);
|
|
printf("\n");
|
|
|
|
delete[] arr;
|
|
|
|
return 0;
|
|
}
|