reversing a string using a for loop C++

Don't ask for the size of string. Apart from not being necessary, it makes your program non-standard, because variable-length array construct, char charray3[sizeOfString], is a compiler extension.

Use std::getline instead, it will allocate read as many characters as necessary. After that, print the string in reverse the same way that you did above, or reverse the string in place if you prefer. Be careful with unsigned subtractions! Your compiler should warn you about it, though.

Note: In case you are wondering why your program does not work, there is a leftover '\n' sitting in the buffer after reading an int. Because of that buffered character, the program returns with an empty string as soon as you call cin>>charray3.

You're re-inventing the wheel :) Use std::string and std::reverse:

#include <algorithm>
#include <iostream>
#include <string>

int main() {
    std::string str{"Hello, World!"};
    std::reverse(str.begin(), str.end());
    std::cout << str << std::endl;
}

Here's a working online example.

you can easily use class string:

#include <iostream>
#include <string>


int main()
{

    std::string s1 = "Hello", s2;

    for(int i(s1.length() - 1 ); i >= 0; i--)
        s2+= s1[i];

    std::cout << s1 << std::endl;
    std::cout << s2 << std::endl;

    return 0;
}

• to solve it in your way using character array the consider:

1- you input the sizeOfString one question: what about the input with cin overflows or underflows the input size (smaller or bigger)???

eg:

sizeOfString = 5;
cin >> charray3; // "ab" now the size is only 3 (+ null terminator)

so writing:

charray3[sizeOfString - 1] = 'c'; // charray3[5 - 1] // charray[4]

while charray4 is not inputted because you inputted only charray3[0] and charray3[1] so as a result a segfault.

to correct it you have to do some extra work:

#include <iostream>
using namespace std;


int main() 
{
     // Reversing A String
    cout << "welcome to string reverser" << endl;
    int sizeOfString;

    cout << "please input size of string" << endl;
    cin >> sizeOfString; // you specified size

    cin.ignore(1, '\n'); // clean the input buffer

    char* charray3 = new char[sizeOfString + 1];
    //cin>>charray3; use getline instead to get whitespaces

    cout << "enter text: " << endl;
    cin.getline(charray3, sizeOfString); // what if the user enter a text smaller or bigger than sizeOfString???
    charray3[sizeOfString] = '\0';
    //to correct it:

    // take effects of input on sizeOfString
    sizeOfString = strlen(charray3);

    cout << "before reversing: " << endl;
    cout << charray3 << endl;
    // to reverse it create a temporary array:

    char* pTmp = new char[sizeOfString + 1];

    for(int i(sizeOfString-1), j = 0; i >= 0; i--, j++)
       pTmp[j] = charray3[i];
    pTmp[sizeOfString] = '\0';

    cout << "after reversing: " << endl;
    cout << pTmp << endl;

    // don't forget to clean:
    delete[] charray3;
    delete[] pTmp;

return 0;
}

// First method
const int MAXLENGTH = 100;
char s[MAXLENGTH];
cin >> s;
int len = strlen(s);
for(int i = 0; i < len/2; i++) {
    char temp = s[i];
    s[i] = s[len-1-i];
    s[len-1-i] = temp;
}
cout << s;

// Second
string s;
cin >> s;
for(int i = 0, len = s.length(); i < len/2; i++) {
    char t = s[i];
    s[i] = s[len-1-i];
    s[len-1-i] = t;
}
cout << s;

The code works now mysteriously. 1) I altered the loop to make it a forwards loop and it worked 2) i reverted back to the problem code and removed the unsigned type.

#include <iostream>
#include <math.h>
#include <iomanip>
#include <sstream>



int main() {


 cout<<"welcome to string reverser"<<endl;
    int sizeOfString;
    cout<<"please input size of string"<<endl;
    cin>>sizeOfString;
    char charray3[sizeOfString];
    cin>>charray3;

    for(int i=sizeOfString-1; i>=0; i--){

    cout<<charray3[i]<<endl;
    }
return 0;
}

Thankyou all for your comments and answers. I will try the variety of alternative code presented.