cppStrCmpStrRevNumStrEtc

#include <iostream>

int strCmp(const char* str1, const char* str2)
{
    size_t len1{ strlen(str1) };
    size_t len2{ strlen(str2) };
    int result{ 0 };

    if (len1 == len2)
    {
        while (*str1 and (*str1 == *str2))
        {
            ++str1;
            ++str2;
        }
        result = *str1 ? 2 : 0;
    }
    else { result = len1 > len2 ? 1 : -1; }

    return result;
}


char* strRev(char* str)
{
    char* head{ str };
    char* tail{ str };

    while (*tail++);
    tail-=2;

    for (char tmp; head < tail; ++head, --tail)
    {
        tmp = *head;
        *head = *tail;
        *tail = tmp;
    }

    return str;
}

char* toUpper(char* str)
{
    const char caseConvert{ 32 };
    char* start{ str };

    for (;*str; ++str)
    {
        if (*str >= 'a' and *str <= 'z') { *str -= caseConvert; }
    }

    return start;
}

char* toLower(char* str)
{
    const char caseConvert{ 32 };
    char* start{ str };

    for (; *str; ++str)
    {
        if (*str >= 'A' and *str <= 'Z') { *str += caseConvert; }
    }

    return start;
}

char* numToStr(int num, char* str)
{
    char tmp;

    for (size_t i{ 0 }; *(str + i) = (num > 0 ? '0' + (num % 10) : 0); num /= 10, ++i);

    for (size_t head{ 0 }, tail{ strlen(str) - 1 }; head < tail; ++head, --tail)
    {
        tmp = *(str + head);
        *(str + head) = *(str + tail);
        *(str + tail) = tmp;
    }

    return str;
}

int strToNum(const char* str)
{
    int num{ 0 };
    for (; *str; num *= 10, num += *str++ - '0');

    return num;
}

int main()
{
    char strA[]{ "Hello!" };
    char strB[]{ "Hello#" };
    char strC[]{ "Hello, world!" };

    char str[]{ "123456" };
    char str1[]{ "Hello!" };
    char str2[]{ "Hello, number 1 (One) WoRlD!" };
    char str3[]{ "Hello, number 1 (One) WoRlD!" };

    std::cout << "Equal: " << std::boolalpha << (strCmp(strA, strA) == 0) << '\n';
    std::cout << "Not equal: " << std::boolalpha << (strCmp(strA, strB) == 2) << '\n';
    std::cout << "First shorter: " << std::boolalpha << (strCmp(strA, strC) == -1) << '\n';
    std::cout << "First longer: " << std::boolalpha << (strCmp(strC, strA) == 1) << '\n';

    std::cout << strRev(str) << '\n';
    std::cout << strRev(str1) << '\n';

    std::cout << toUpper(str) << '\n';
    std::cout << toUpper(str1) << '\n';
    std::cout << toUpper(str2) << '\n';

    std::cout << toLower(str) << '\n';
    std::cout << toLower(str1) << '\n';
    std::cout << toLower(str3) << '\n';

    char strBuf[10];
    std::cout << numToStr(26907, strBuf) << '\n';
    std::cout << strToNum(strBuf) << '\n';

    return 0;
}