Splitting a string by a character

Question

I know this is a quite easy problem but I just want to solve it for myself once and for all

I would simply like to split a string into an array using a character as

Answer 1

Another way (C++11/boost) for people who like RegEx. Personally I'm a big fan of RegEx for this kind of data. IMO it's far more powerful than simply splitting strings using a delimiter since you can choose to be be a lot smarter about what constitutes "valid" data if you wish.

#include <string>
#include <algorithm>    // copy
#include <iterator>     // back_inserter
#include <regex>        // regex, sregex_token_iterator
#include <vector>

int main()
{
    std::string str = "08/04/2012";
    std::vector<std::string> tokens;
    std::regex re("\\d+");

    //start/end points of tokens in str
    std::sregex_token_iterator
        begin(str.begin(), str.end(), re),
        end;

    std::copy(begin, end, std::back_inserter(tokens));
}

Answer 2

Is there a reason you don't want to convert a string to a character array (char*) ? It's rather easy to call .c_str(). You can also use a loop and the .find() function.

string class
string .find()
string .c_str()

Answer 3

Using vectors, strings and stringstream. A tad cumbersome but it does the trick.

std::stringstream test("this_is_a_test_string");
std::string segment;
std::vector<std::string> seglist;

while(std::getline(test, segment, '_'))
{
   seglist.push_back(segment);
}

Which results in a vector with the same contents as

std::vector<std::string> seglist{ "this", "is", "a", "test", "string" };

Answer 4

What about erase() function? If you know exakt position in string where to split, then you can "extract" fields in string with erase().

std::string date("01/02/2019");
std::string day(date);
std::string month(date);
std::string year(date);

day.erase(2, string::npos); // "01"
month.erase(0, 3).erase(2); // "02"
year.erase(0,6); // "2019"

Answer 5

I inherently dislike stringstream, although I'm not sure why. Today, I wrote this function to allow splitting a std::string by any arbitrary character or string into a vector. I know this question is old, but I wanted to share an alternative way of splitting std::string.

This code omits the part of the string you split by from the results altogether, although it could be easily modified to include them.

#include <string>
#include <vector>

void split(std::string str, std::string splitBy, std::vector<std::string>& tokens)
{
    /* Store the original string in the array, so we can loop the rest
     * of the algorithm. */
    tokens.push_back(str);

    // Store the split index in a 'size_t' (unsigned integer) type.
    size_t splitAt;
    // Store the size of what we're splicing out.
    size_t splitLen = splitBy.size();
    // Create a string for temporarily storing the fragment we're processing.
    std::string frag;
    // Loop infinitely - break is internal.
    while(true)
    {
        /* Store the last string in the vector, which is the only logical
         * candidate for processing. */
        frag = tokens.back();
        /* The index where the split is. */
        splitAt = frag.find(splitBy);
        // If we didn't find a new split point...
        if(splitAt == string::npos)
        {
            // Break the loop and (implicitly) return.
            break;
        }
        /* Put everything from the left side of the split where the string
         * being processed used to be. */
        tokens.back() = frag.substr(0, splitAt);
        /* Push everything from the right side of the split to the next empty
         * index in the vector. */
        tokens.push_back(frag.substr(splitAt+splitLen, frag.size()-(splitAt+splitLen)));
    }
}

To use, just call like so...

std::string foo = "This is some string I want to split by spaces.";
std::vector<std::string> results;
split(foo, " ", results);

You can now access all the results in the vector at will. Simple as that - no stringstream, no third party libraries, no dropping back to C!

Answer 6

Boost has the split() you are seeking in algorithm/string.hpp:

std::string sample = "07/3/2011";
std::vector<string> strs;
boost::split(strs, sample, boost::is_any_of("/"));