Question

I looked everywhere and can’t find an answer to this specific question 🙁

I have a string date, which contains the date with all the special characters stripped away. (i.e : yyyymmddhhmm or 201212031204).

I’m trying to convert this string into an int to be able to sort them later. I tried atoi, did not work because the value is too high for the function. I tried streams, but it always returns -858993460 and I suspect this is because the string is too large too. I tried atol and atoll and they still dont give the right answer.

I’d rather not use boost since this is for a homework, I dont think i’d be allowed.

Am I out of options to convert a large string to an int ?
Thank you!

What i’d like to be able to do :

int dateToInt(string date)
{
date = date.substr(6,4) + date.substr(3,2) + date.substr(0,2) + date.substr(11,2) + date.substr(14,2);
int d;
d = atoi(date.c_str());
return d;

}

Answer 1

You’re on the right track that the value is too large, but it’s not just for those functions. It’s too large for an int in general. ints only hold up to 32 bits, or a maximum value of 2147483647 (4294967295 if unsigned). A long long is guaranteed to be large enough for the numbers you’re using. If you happen to be on a 64-bit system, a long will be too.

Now, if you use one of these larger integers, a stream should convert properly. Or, if you want to use a function to do it, have a look at atoll for a long long or atol for a long. (Although for better error checking, you should really consider strtoll or strtol.)

Completely alternatively, you could also use a time_t. They’re integer types under the hood, so you can compare and sort them. And there’s some nice functions for them in <ctime> (have a look at http://www.cplusplus.com/reference/ctime/).