Сложение и вычитание двух больших чисел в столбик

#include <iostream>
#include <cstdint>
 
using namespace std;
 
void print(uint8_t n[10])
{
    int i;
    for (i = 0; i < 9 && n[i] == 0; ++i);
    for (; i < 10; ++i) cout << static_cast<uint16_t>(n[i]);
    cout << endl;
}
 
int main()
{
    uint8_t x[10] = { 1, 2, 3, 4, 5, 6, 4, 8, 9, 0 }, y[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 }, z[10];
    uint8_t c = 0;
    int i;
    
    for (i = 9; i >=0 ; --i)
    {
        c += x[i] + y[i];
        z[i] = c % 10;
        c /= 10;
    }
    
    print(x);
    print(y);
    print(z);
}

#include <iostream>
#include <cctype>
 
#define MAX_SIZE 50
#define END_DIGIT -1
 
typedef short LongNumber[MAX_SIZE];
 
//-----------------------------------------------------------------------------
unsigned readLongNumber(LongNumber number) {
    static unsigned size = 0;
    static unsigned pos = 0;
    char ch = std::cin.get();
 
    if (::isdigit(ch) && (pos < MAX_SIZE - 1)) {
        pos++;
        size = readLongNumber(number);
        number[size - (pos--)] = ch - '0';
    } else {
        number[pos] = END_DIGIT;
        size = pos;
    }
    return size;
}
//-----------------------------------------------------------------------------
void printLongNumber(const LongNumber number) {
    if (*number != END_DIGIT) {
        printLongNumber(number + 1);
        std::cout << *number;
    }
}
//-----------------------------------------------------------------------------
unsigned lengthLongNumber(const LongNumber number) {
    return (*number != -1) ? 1 + lengthLongNumber(number + 1) : 0;
}
//-----------------------------------------------------------------------------
int compareLongNumber(const LongNumber srcA, const LongNumber srcB) {
    unsigned sizeA = lengthLongNumber(srcA);
    unsigned sizeB = lengthLongNumber(srcB);
 
    if (sizeA != sizeB) {
        return (sizeA < sizeB) ? 1 : -1;
    }
 
    for (int i = sizeA - 1; 0 <= i; --i) {
        unsigned cmp = srcA[i] - srcB[i];
        if (cmp) {
            return (cmp < 0) ? 1 : -1;
        }
    }
 
    return 0;
}
//-----------------------------------------------------------------------------
void summLongNumber(LongNumber dest, LongNumber srcA, LongNumber srcB) {
    unsigned sizeA = lengthLongNumber(srcA);
    unsigned sizeB = lengthLongNumber(srcB);
    unsigned size = sizeA < sizeB ? sizeB : sizeA;
 
    unsigned dec = 0;
    for (unsigned i = 0; i < size; ++i) {
        short a = (i < sizeA) ? srcA[i] : 0;
        short b = (i < sizeB) ? srcB[i] : 0;
        short sum = a + b + dec;
 
        dec = (10 <= sum);
        dest[i] = dec ? (sum - 10) : sum;
    }
 
    if (size < MAX_SIZE - dec) {
        if (dec) {
            dest[size] = 1;
        }
        dest[size + dec] = END_DIGIT;
    } else {
        dest[MAX_SIZE - 1] = END_DIGIT;
    }
}
//-----------------------------------------------------------------------------
void subLongNumber(LongNumber dest, LongNumber srcA, LongNumber srcB) {
    int cmp = compareLongNumber(srcA, srcB);
 
    short* arrA = (cmp < 0) ? srcA : srcB;
    short* arrB = (cmp < 0) ? srcB : srcA;
 
    unsigned sizeA = lengthLongNumber(arrA);
    unsigned sizeB = lengthLongNumber(arrB);
    unsigned dec = 0;
    for (unsigned i = 0; i < sizeA; ++i) {
        short a = arrA[i];
        short b = (i < sizeB) ? arrB[i] : 0;
        short sub = a - b - dec;
 
        dec = (sub < 0);
        dest[i] = dec ? (sub + 10) : sub;
    }
 
    unsigned i = sizeA - 1;
    for (; (0 < i) && (dest[i] == 0); --i) { ; }
    dest[i + 1] = END_DIGIT;
}
//-----------------------------------------------------------------------------
 
int main() {
    LongNumber a, b, c, d;
 
    std::cout << "first long number: ";
    readLongNumber(a);
 
    std::cout << "second long number: ";
    readLongNumber(b);
 
    int cmp = compareLongNumber(a, b);
    std::cout << "compare: " << ((cmp < 0) ? "first" : (0 < cmp) ? "second" : "equals") << std::endl;
 
    summLongNumber(c, a, b);
    std::cout << "summ: ";
    printLongNumber(c); std::cout << std::endl;
 
    subLongNumber(d, a, b);
    std::cout << "sub: ";
    printLongNumber(d); std::cout << std::endl;
 
    return 0;
}