c++ converting string to int

Question

//sLine is the string
for(int l = 0; l < sLine.length(); l++)
{
    string sNumber;
    if(sLine[l] == \'-\')
    {   
        sNumber.push_back(sLine[l]);
        sN         


        

Answer 1

You output extra 0 for the characters which are not digits. The problem is that atoi returns 0 when it cannot convert the input, so your whitespaces are printed as zeroes.

Answer 2

Move this:

const char* testing = sNumber.c_str();
int num = atoi(testing);
cout << num;

Below the last } in the code you pasted, i.e. out of the for-loop. Currently you get a separate printout for every character in sLine because it's executed on every iteration of the loop. (The last character in sLine may be a linefeed so this can occur even if you think you wrote only one digit.)

Edit: Also move the declaration of sNumber above the for-loop.

You may also want to change if (sLine[l] == '-') to if (sLine[l] == '-' && (l + 1) < sLine.length()) so you don't access beyond the end of the string if the dash is the final character on the line.

You may also want to rename the variable l to something that looks less like a 1. =)

You may also want to rethink if this is the right way to do this at all (usually if a simple thing gets this complicated, chances are you're doing it wrong).

Answer 3

That seems like a painful way to recreate the wheel. You'd be better off using a stringstream to parse this.

std::stringstream strm(sLine);
int num;
while(strm >> num)
{
    std::cout << num << std::endl;
}

Answer 4

It's displaying a zero for all nonrecognized characters, because atoi returns 0 when given a non-numeric string (like a space!)

However, what you want to do, is shockingly simple:

std::stringstream ss(sLine);
int num;
while(ss >> num) {
    cout << num;
}