sort.c

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

#define ARRAY_SIZE 1000000

int compare(const void *a, const void *b)
{
    int ia = *(int*)a;
    int ib = *(int*)b;
    return ia - ib;
}

int main(void)
{
    FILE *unsorted = fopen("unsorted.txt", "r");
    if (unsorted == NULL) {
        puts("failed to open unsorted.txt");
        return 1;
    }
    int *array = malloc(ARRAY_SIZE * sizeof(int));
    if (array == NULL) {
        puts("malloc failed");
        return 1;
    }
    for (int i = 0; i < ARRAY_SIZE; i++) {
        fscanf(unsorted, "%d", &array[i]);
    }
    fclose(unsorted);
    struct timespec start, end;
    clock_gettime(CLOCK_MONOTONIC, &start);
    qsort(array, ARRAY_SIZE, sizeof(int), compare);
    clock_gettime(CLOCK_MONOTONIC, &end);
    FILE *sorted = fopen("sorted.txt", "w");
    for (int i = 0; i < ARRAY_SIZE; i++) {
        fprintf(sorted, "%d\n", array[i]);
    }
    fclose(sorted);
    free(array);
    uint64_t nanoseconds = end.tv_sec - start.tv_sec;
    nanoseconds *= 1000000000;
    nanoseconds += end.tv_nsec - start.tv_nsec;
    double miliseconds = (double)nanoseconds / 1000000.0;
    printf("qsort took %fms\n", miliseconds);
    return 0;
}