/*
 * Program to test sort function: 
 * Generate a random sequence of N integers, sort them, and check
 * that the sort succeeded.  
 * This version gets N from a command-line argument and uses malloc() to get
 * space for the array.  It sorts using a selection sort.
 */
#include <stdio.h>
#include <stdlib.h>

/* function declarations */
void fill_with_random(int nums[], int size);
void sort(int nums[], int size);
void sort_check(int nums[], int size);

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

    int N;
    char* endptr;

    /* get number of elements to sort */
    if (argc < 2) {
        fprintf(stderr, "usage:  %s numToSort\n", argv[0]);
        return EXIT_FAILURE;
    }
    N = strtol(argv[1], &endptr, 10);
    if (*endptr != '\0') {
        fprintf(stderr, "usage:  %s numToSort\n", argv[0]);
        return EXIT_FAILURE;
    }

    /* allocate space for array */
    int * nums = malloc(sizeof(*nums) * N);
    if (nums == NULL) {
        fprintf(stderr, "could not allocate space for %d ints\n", N);
        return EXIT_FAILURE;
    }

    /* fill, sort, check as before */
    fill_with_random(nums, N);
    sort(nums, N);
    sort_check(nums, N);

    /* free allocated space */
    free(nums);

    return EXIT_SUCCESS;
}

/* 
 * fills nums[0 .. size-1] with a random sequence of integers 
 */
void fill_with_random(int nums[], int size) {
    for (int i = 0; i < size; ++i) {
        nums[i] = rand();
        /* printf("%d\n", nums[i]); */
    }
}

/* 
 * prints "sort succeeded" if nums[0 .. size-1] is in order,
 * "sort failed" if not 
 */
void sort_check(int nums[], int size) {
    for (int i = 0; i < size-1 ; ++i) {
        if (!(nums[i] <= nums[i+1])) {
            printf("sort failed\n");
            return;
        }
    }
    printf("sort succeeded\n");
}

/* gets index of smallest element of nums[start .. size-1] */
int index_of_smallest(int nums[], int size, int start) {
    int smallest = start;
    for (int i = start+1; i < size; ++i) {
        if (nums[i] < nums[smallest])
            smallest = i;
    }
    return smallest;
}	
/*
 * sorts nums[0 .. size-1]
 */
void sort(int nums[], int size) { 
    for (int i = 0; i < size-1; ++i) {
        int k = index_of_smallest(nums, size, i);
        if (k != i) {
            int temp = nums[k];
            nums[k] = nums[i];
            nums[i] = temp;
        }
    }
}