digitcount.py: the C version

/* This is a C port of digitcount.py, proving that in the hands
 * of a capable programmer, C can be just as high level as Python.
 */

#include <stdio.h>

void
aswap(int *array, int a, int b)
{
    int temp = array[a];

    array[a] = array[b];
    array[b] = temp;
}

void
sync_sort(int *array1, int *array2)
{
    int alen = *array1,
        *list1 = array1 + 1,
        *list2 = array2 + 1,
        i, j, swapped;

    for(i = 0; i < alen; i++){
        swapped = 0;

        for(j = alen - 1; j > i; j--){
            if(list1[j] < list1[j - 1]){
                aswap(list1, j, j - 1);
                aswap(list2, j, j - 1);
                swapped = 1;
            }
        }

        if(!swapped)
            break;
    }
}

int *
count(char *str)
{
    static int digits[11] = {0};

    digits[0] = 10;

    while(*str){
        digits[1 + (*str) - '0'] += 1;
        str++;
    }

    return digits;
}

void
report(int *digits, int *digit_nums)
{
    int alen = *digits,
        i;

    for(i = 0; i < alen; i++){
        printf("%i: %i\n", digit_nums[1 + i], digits[1 + i]);
    }
}

void
init_digit_nums(int *digit_nums)
{
    int i;

    for(i = 0; i < 10; i++)
        digit_nums[1 + i] = i;

    digit_nums[0] = i;
}

void
areverse(int *array)
{
    int array2[11] = {0},
        *list1 = array + 1,
        *list2 = array2 + 1,
        i;

    for(i = (*array) - 1; i >= 0; i--){
        *list2 = list1[i];
        list2++;
    }

    list2 = array2 + 1;

    for(i = 0; i < *array; i++){
        list1[i] = *list2;
        list2++;
    }
}

int
main(int argc, char **argv)
{
    int *digits = count(argv[1]),
        digit_nums[11];

    init_digit_nums(digit_nums);

    printf("By digit:\n");
    report(digits, digit_nums);

    printf("By frequency:\n");
    sync_sort(digits, digit_nums);
    areverse(digit_nums);
    areverse(digits);
    report(digits, digit_nums);
}