/*
 * Program to test sort function: 
 * Generate a random sequence of N integers, sort them, and check
 * that the sort succeeded.  
 * This version gets N and a seed for generating the random sequence 
 * from command-line arguments, allocates space for the integers dynamically, 
 * and uses library function qsort() for the sort.
 */
#include <stdio.h>
#include <stdlib.h>

/* function declarations -- see definitions (at end) for more comments */
void fill_with_random(int a[], int size);
void sort(int a[], int size);
void print(int a[], int size);
int find_out_of_order(int a[], int size);

/* comparison function to pass to qsort */
int compare(const void *e1, const void *e2);

/* main program */
int main(int argc, char *argv[]) {

    int * data; /* will point to dynamically allocated array */

    int count;
    int seed;
	char *endptr;	

    /* get count, seed from command-line arguments */

    if (argc != 3) {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}

	count = strtol(argv[1], &endptr, 10);
	if (*endptr != '\0') {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}

	seed = strtol(argv[2], &endptr, 10);
	if (*endptr != '\0') {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}

    if ((count <= 0) || (seed <= 0)) {
        printf("values must not be negative\n");
        return EXIT_FAILURE;
    }

    /* allocate space for array */

    if ((data = malloc(sizeof(data[0]) * count)) == NULL) {
        printf("unable to allocate space for %d values\n", count);
        return EXIT_FAILURE;
    }

    /* fill with random data, sort, check, as before */

    srand(seed);
    fill_with_random(data, count);
    /* uncomment if you want to print */
    /* print(data, count) */
    sort(data, count);
    /* uncomment if you want to print */
    /* print(data, count) */
    int out_of_order = find_out_of_order(data, count);
    if (out_of_order < 0) {
        printf("sorted\n");
    }
    else {
        printf("not sorted\n");
        printf("first out-of-order element at index %d\n", out_of_order);
    }

    /* free array */

    free(data);

    return EXIT_SUCCESS;
}

/* fill array with randomly generated data */
void fill_with_random(int a[], int size) {
    for (int i = 0; i < size; ++i) {
        a[i] = rand();
    }
}

/* print array */
void print(int a[], int size) {
	for (int i=0; i < size; ++i) {
		printf("%d\n", a[i]);
	}
}

/* 
 * check whether array is sorted:
 * returns index of first out-of-order element, or -1 if all are in order
 */
int find_out_of_order(int a[], int size) {
    for (int i = 0; i < size-1; ++i) {
        if (a[i] > a[i+1]) { 
            return i;
        }
    }
    return -1;
}

/* sort array */
void sort(int a[], int size) {
    qsort(a, size, sizeof(a[0]), &compare);
}

/* comparison function to pass to qsort */
int compare(const void *e1, const void *e2) {
    int *i1 = (int *) e1;
    int *i2 = (int *) e2;
    if (*i1 < *i2)
        return -1;
    else if (*i1 > *i2)
        return 1;
    else
        return 0;
}