extracting a file name from file path in c++

I have a string storing path of a file and I'm doing some string processing, indexing of a std::string object, but output string is strange, code:

#include<iostream>
#include<string>

using namespace std;

int main()
{
    string x = "C:\\Users\\lenovo\\Desktop\\QBFdata.txt";
    string temp = "";
    for(int  i = x.length() - 1; i > 0; i--)
    {
        if(x[i] == '\\')
            break;
        else
            temp.append(&x[i]);
    }
 cout << temp << "\n";
}

but output is strange apparently it append the contents of temp again to it.

txttxt.txta.txtta.txtata.txtdata.txtFdata.txtBFdata.txtQBFdata.txt

Please don't suggest any alternatives to this because I already have a solution

int main()
{
    string x = "C:\\Users\\NK\\Desktop\\QBFdata.txt";
    int pos = x.find_last_of('\\');
    string temp = x.substr(pos + 1);
    cout << temp;
}

It works fine.

I want to know what is the problem in the first code.

Thanks.

I'm using codeblocks 16.01

Solution

As others have stated, the problem is that you are using the wrong overload of std::string::append(), so you are appending whole substrings, not individual characters, on each loop iteration.

To append a single character at a time, use one of these instead:

temp.append(&x[i], 1);

temp.push_back(x[i]);

temp += x[i];

However since you are looping backwards, you need to prepend each character in the FRONT of the string instead of append to the BACK:

temp.insert(0, &x[i], 1);

temp = x[i] + temp;