/*
 * 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> /* has EXIT_SUCCESS, EXIT_FAILURE */

/* 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);
int int_compare(const void * e1, const void * e2);

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

	/* get count, seed from command-line arguments */
	if (argc != 3) {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}
	int count;
	int seed;
	char *endptr;	
	count = strtol(argv[1], &endptr, 10);
	if (*endptr != '\0') {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}
	if ((count < 1) ) {
		printf("count must at least 1\n");
		return EXIT_FAILURE;
	}

	seed = strtol(argv[2], &endptr, 10);
	if (*endptr != '\0') {
		printf("usage %s count seed\n", argv[0]);
		return EXIT_FAILURE;
	}
	if ((seed <= 0)) {
		printf("seed must not be negative\n");
		return EXIT_FAILURE;
	}

	/* allocate space for array dynamically */

	/* int data[MAX_COUNT]; */
	int * data = malloc(count * sizeof(data[0]));
	if (data == NULL) {
		printf("cannot get space for %d ints\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]), &int_compare);
}

/* comparison function for sort */
int int_compare(const void * e1, const void * e2) {
	const int * i1 = (const int *) e1;
	const int * i2 = (const int *) e2;
	if (*i1 < *i2)
		return -1;
	else if (*i1 > *i2)
		return 1;
	else
		return 0;
}