How to use new and delete operator in C

0 votes

I'm presently studying C++ and have completed the following task in which I must transform an array from uppercase to lowercase and vice versa:

int main()
{
    char str[100];
    cout << "Enter anything: ";
    cin.getline(str, 100);

    //upper to lower vice versa
    for (int i = 0; i < 100; i++) {
        if (str[i] == 0x20)
        {
            continue;
        }
        str[i] ^= 0x20;
    }
    cout << "output: " << str;

return 0;

}

However, they want me to use the new[] and delete[] operators instead of declaring the numbers in an array, which is what this portion char str[100]; does. I've attempted to use it, but the notion confuses me. Is there anything you might suggest? Any assistance will be much appreciated! Thank you so much in advance!

Jun 15, 2022 in C++ by Nicholas
• 7,760 points
103 views

1 answer to this question.

0 votes
int main(){
    char *str;
    int sz = 0;

    std::cout << "enter number of characters: ";
    std::cin >> sz;

    str = new char[sz + 1];

    std::cout << "Enter anything: ";
    std::cin.ignore();
    std::cin.getline(str, sz + 1);

    //upper to lower vice versa
    for (int i = 0; i < sz; i++) {
        if (str[i] == 0x20)
        {
            continue;
        }
        str[i] ^= 0x20;
    }
    std::cout << "output: " << str;

    delete[] str;
    return 0;
}

You allocate memory on the heap with new, and you deallocate memory with delete[].

Because the getline appends the 0 character at the end, you must set the array size to sz + 1.

answered Jun 20, 2022 by Damon
• 4,960 points

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