/**
 * Program to test sorting function:
 *
 * Generate array of N random values.
 * Sort the array, counting how many comparisons were performed.
 *   (This isn't essential to doing the sort, but the results may
 *   be interesting.)
 * Check that the result is sorted.
 *
 * Input:  Number of elements.
 * Output:  Whether sort worked, and the numbers of comparisons.
 */
#include <stdio.h>
#include <stdlib.h>

/* Function declarations.  (Comments with definitions, below main.) */
void fill(int nums[], int size);
void sort(int nums[], int size);
void check(int nums[], int size);

/* Main program. */
int main(void) {

	int N;
	int * nums;

	/* get N from user */
	printf("Enter how many numbers to generate and sort:\n");
	if (scanf("%d", &N) != 1) {
		printf("Error -- not a number\n");
		/* bail out of program with return code indicating error */
		exit(EXIT_FAILURE);
	}

	/* try to get memory for array of N ints */
	nums = malloc(sizeof(int) * N);
	if (nums == NULL) {
		printf("Error -- not enough memory for %d numbers\n", N);
		/* bail out of program with return code indicating error */
		exit(EXIT_FAILURE);
	}

	/* fill with random numbers, sort, and check result */
	fill(nums, N);
	sort(nums, N);
	check(nums, N);

	/* release allocated memory */
	free(nums);

	/* return value indicates success (same as "return 0" but perhaps
	 * more readable
	 */
	return EXIT_SUCCESS;
}
/*
 * Fill array with random numbers.  
 * "size" is the size of array "nums".
 */
void fill(int nums[], int size) {
	int i;
	for (i = 0; i < size; ++i) {
		nums[i] = rand();
	}
}

/*
 * Sort array and print number of comparisons done.  (This isn't essential
 * to getting the array put in order, but results may be interesting.) 
 *
 * "size" is the size of array "nums".
 */
void sort(int nums[], int size) {
	int i, j, temp;
	int comparisons = 0;

	/* bubble sort */

	for (i = 0; i < size-1; ++i) {

		/* go through elements from 0 through size-1-i, switching pairs
 		 * that are out of order.
 		 * (why size-1-i?  because the first time through we end up with
 		 * the last element in the right place, the next time through 
		 * with the last 2 elements in the right place, etc.
                 */
		for (j = 0; j < size-1-i; ++j) {
			++comparisons;

			/* for each pair of adjacent elements, switch if out of 
			 * order 
			 */
			if (nums[j] > nums[j+1]) {
				temp = nums[j];
				nums[j] = nums[j+1];
				nums[j+1] = temp;
			}
		}
	}
	printf("Sorting %d numbers required %d comparisons\n",
			size, comparisons);
}

/*
 * Check whether array is in order and print result.  
 * "size" is the size of array "nums".
 */
void check(int nums[], int size) {
	int i;
	for (i = 0; i < size-1; ++i) {
		if (nums[i] > nums[i+1]) {
			printf("Sort failed -- numbers are not in order\n");
			return;
		}
	}
	printf("Sort succeeded -- numbers are in order\n");
}