50007. Yard, Foot, and Inch

int get_inches(int arr[3]){
    return arr[0] * 36 + arr[1] * 12 + arr[2];
}

void deal_inches(int arr[3], int l){
    arr[0] = l / 36; l %= 36;
    arr[1] = l / 12; l %= 12;
    arr[2] = l;
}

void init(int arr[3]){
    for(int i = 0; i < 3; i++) arr[i] = 0;
}
void add(int arr[3], int l){
    deal_inches(arr, get_inches(arr) + l);
}
void sum(int arr_a[3], int arr_b[3], int arr_c[3]){
    deal_inches(arr_c, get_inches(arr_a) + get_inches(arr_b));
}
void diff(int arr_a[3], int arr_b[3], int arr_c[3]){
    deal_inches(arr_c, get_inches(arr_a) - get_inches(arr_b));
}

void init(int arr[3]);
void add(int arr[3], int l);
void sum(int arr_a[3], int arr_b[3], int arr_c[3]);
void diff(int arr_a[3], int arr_b[3], int arr_c[3]);