quicksort.c (lab07)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_ELEMENT 99

void quicksort_rec(int array[], int start, int end, int pivot);
int partition (int array[], int start, int end, int pivot);
void swap(int *origin, int *end);
int medOfThree(int array[], int random_1, int random_2, int random_3);

int main (int argc, char *argv[]) {
    int entry_element = 0, counter, entry_size = 0;
    int array[MAX_ELEMENT];
    printf("Enter data size: ");
    scanf("%d", &entry_size);
    printf("Enter data: \n");
    for (counter = 0; counter < entry_size; counter++) {
        scanf("%d", &array[counter]);
    }
    if (!strcmp(argv[1], "-pn")) {
        printf("Sorted with naive pivot:\n");
        quicksort_rec(array, 0, entry_size - 1, array[0]);

    } else if (!strcmp(argv[1], "-pm")) {
        printf("Sorted with median of three pivot:\n");
        int random_1 = rand() % (entry_size - 1);
        int random_2 = rand() % (entry_size - 1);
        int random_3 = rand() % (entry_size - 1);
        int median = medOfThree(array, random_1, random_2, random_3);
        quicksort_rec(array, 0, entry_size - 1, median);

    } else if (!strcmp(argv[1], "-pr")) {
        printf("Sorted with randomized pivot: \n");
        int random = rand() % (entry_size - 1);
        quicksort_rec(array, 0, entry_size - 1, array[random]);

    }
    for (counter = 0; counter < entry_size; counter++) {
        if (counter != entry_size - 1) {
            printf("%d ", array[counter]);
        } else {
            printf("%d\n", array[counter]);
        }
    }
    return EXIT_SUCCESS;
}

void quicksort_rec(int array[], int start, int end, int pivot) {
    if (start < end) {
        int pivot_qs = partition(array, start, end, pivot);
        quicksort_rec(array, start, pivot_qs - 1, pivot);
        quicksort_rec(array, pivot_qs + 1, end, pivot);
    }
}

int partition (int array[], int start, int end, int pivot) {
    int index_swap_1 = start - 1;
    for (int index_swap_2 = start; index_swap_2 <= end - 1; index_swap_2++) {
        if (array[index_swap_2] <= pivot) {
            index_swap_1++;
            swap(&array[index_swap_1], &array[index_swap_2]);
        }
    }
    swap(&array[index_swap_1 + 1], &array[end]);
    return index_swap_1 + 1;
}

void swap(int *origin, int *end) {
    int swap_var = *origin;
    *origin = *end;
    *end = swap_var;
}

int medOfThree(int array[], int random_1, int random_2, int random_3) {
    if (array[random_1] <= array[random_2] && array[random_1] >= array[random_3]) {
        return array[random_1];
    } else if (array[random_2] <= array[random_1] && array[random_2] >= array[random_3]) {
        return array[random_2];
    } else {
        return array[random_3];
    }
}