How can I convert a std::string to int?

Question

Just have a quick question. I've looked around the internet quite a bit and I've found a few solutions but none of them have worked yet. Looking at converting a string to an int and I don't mean ASCII codes. For a quick run-down, we are passed in an equation as a string. We are to break it down, format it correctly and solve the linear equations. Now, in saying that, I'm not able to convert a string to an int. I know that the string will be in either the format (-5) or (25) etc. so it's definitely an int. But how do we extract that from a string? One way I was thinking is running a for/while loop through the string, check for a digit, extract all the digits after that and then look to see if there was a leading '-', if there is, multiply the int by -1. It seems a bit over complicated for such a small problem though. Any ideas?

Answer 1

So many questions, but first off -- does the string contain more than just the numbers you're trying to convert? The function atoi() is the easiest way to convert, even with a minus sign, but if there is other text involved then you'll have to parse out the values you want (I'd suggest looking into regex but that's a heady can of worms you won't want to open).