Right way to split an std::string into a vector

Question

What is the right way to split a string into a vector of strings? Delimiter is space or comma.

Answer 1

A convenient way would be boost's string algorithms library.

#include <boost/algorithm/string/classification.hpp> // Include boost::for is_any_of
#include <boost/algorithm/string/split.hpp> // Include for boost::split
// ...

std::vector<std::string> words;
std::string s;
boost::split(words, s, boost::is_any_of(", "), boost::token_compress_on);

Answer 2

For space separated strings, then you can do this:

std::string s = "What is the right way to split a string into a vector of strings";
std::stringstream ss(s);
std::istream_iterator<std::string> begin(ss);
std::istream_iterator<std::string> end;
std::vector<std::string> vstrings(begin, end);
std::copy(vstrings.begin(), vstrings.end(), std::ostream_iterator<std::string>(std::cout, "\n"));

Output:

What
is
the
right
way
to
split
a
string
into
a
vector
of
strings

---

string that have both comma and space

struct tokens: std::ctype<char> 
{
    tokens(): std::ctype<char>(get_table()) {}
 
    static std::ctype_base::mask const* get_table()
    {
        typedef std::ctype<char> cctype;
        static const cctype::mask *const_rc= cctype::classic_table();
 
        static cctype::mask rc[cctype::table_size];
        std::memcpy(rc, const_rc, cctype::table_size * sizeof(cctype::mask));
 
        rc[','] = std::ctype_base::space; 
        rc[' '] = std::ctype_base::space; 
        return &rc[0];
    }
};
 
std::string s = "right way, wrong way, correct way";
std::stringstream ss(s);
ss.imbue(std::locale(std::locale(), new tokens()));
std::istream_iterator<std::string> begin(ss);
std::istream_iterator<std::string> end;
std::vector<std::string> vstrings(begin, end);
std::copy(vstrings.begin(), vstrings.end(), std::ostream_iterator<std::string>(std::cout, "\n"));

Output:

right
way
wrong
way
correct
way

Answer 3

You can use getline with delimiter:

string s, tmp; 
stringstream ss(s);
vector<string> words;

while(getline(ss, tmp, ',')){
    words.push_back(tmp);
    .....
}

Answer 4

vector<string> split(string str, string token){
    vector<string>result;
    while(str.size()){
        int index = str.find(token);
        if(index!=string::npos){
            result.push_back(str.substr(0,index));
            str = str.substr(index+token.size());
            if(str.size()==0)result.push_back(str);
        }else{
            result.push_back(str);
            str = "";
        }
    }
    return result;
}

split("1,2,3",",") ==> ["1","2","3"]

split("1,2,",",") ==> ["1","2",""]

split("1token2token3","token") ==> ["1","2","3"]

Answer 5

If the string has both spaces and commas you can use the string class function

found_index = myString.find_first_of(delims_str, begin_index) 

in a loop. Checking for != npos and inserting into a vector. If you prefer old school you can also use C's

strtok() 

method.

Answer 6

std::vector<std::string> split(std::string text, char delim) {
    std::string line;
    std::vector<std::string> vec;
    std::stringstream ss(text);
    while(std::getline(ss, line, delim)) {
        vec.push_back(line);
    }
    return vec;
}

split("String will be split", ' ') -> {"String", "will", "be", "split"}

split("Hello, how are you?", ',') -> {"Hello", "how are you?"}

EDIT: Here's a thing I made, this can use multi-char delimiters, albeit I'm not 100% sure if it always works:

std::vector<std::string> split(std::string text, std::string delim) {
    std::vector<std::string> vec;
    size_t pos = 0, prevPos = 0;
    while (1) {
        pos = text.find(delim, prevPos);
        if (pos == std::string::npos) {
            vec.push_back(text.substr(prevPos));
            return vec;
        }

        vec.push_back(text.substr(prevPos, pos - prevPos));
        prevPos = pos + delim.length();
    }
}

Answer 7

Tweaked version from Techie Delight:

#include <string>
#include <vector>

std::vector<std::string> split(const std::string& str, char delim) {
    std::vector<std::string> strings;
    size_t start;
    size_t end = 0;
    while ((start = str.find_first_not_of(delim, end)) != std::string::npos) {
        end = str.find(delim, start);
        strings.push_back(str.substr(start, end - start));
    }
    return strings;
}

Answer 8

Here is my variant that work somelike as explode function in PHP, we provide given string and delimiters list.

std::vector< std::string > explode(const std::string& data, const std::string& delimiters) {
    auto is_delim = [&](auto & c) { return delimiters.find(c) != std::string::npos; };
    std::vector< std::string > result;
    for (std::string::size_type i(0), len(data.length()), pos(0); i <= len; i++) {
        if (is_delim(data[i]) || i == len) {
            auto tok = data.substr(pos, i - pos);
            if ( !tok.empty() )
                result.push_back( tok );
            pos = i + 1;
        }
    } return result;
}

example of usage

std::string test_delimiters("hello, there is lots of, delimiters, that may be even together,  ");

auto dem_res = explode(test_delimiters, " ,"); // space or comma

for (auto word : dem_res) {
    std::cout << word << '\n';
} std::cout << "end\n";

the ouput:

hello
there
is
lots
of
delimiters
that
may
be
even
together
end

Answer 9

i made this custom function that will convert the line to vector

#include <iostream>
#include <vector>
#include <ctime>
#include <string>

using namespace std;

int main(){

    string line;
    getline(cin, line);
    int len = line.length();
    vector<string> subArray;

    for (int j = 0, k = 0; j < len; j++) {
        if (line[j] == ' ') {
            string ch = line.substr(k, j - k);
            k = j+1;
            subArray.push_back(ch);
        }
        if (j == len - 1) {
            string ch = line.substr(k, j - k+1);
            subArray.push_back(ch);
        }
    }

    return 0;
}

Answer 10

Here is a modified version of roach's solution that splits based on a string of single character delimiters + supports the option to compress duplicate delimiters.

std::vector<std::string> split(std::string text, std::string delim, bool compress) 
{
    std::vector<std::string> vec;
    size_t pos = 0, prevPos = 0;
    while (1) 
    {
        pos = text.find_first_of(delim, prevPos);

        while(compress) 
        {
            if( prevPos == pos )
                prevPos++;
            else
                break;

            pos = text.find_first_of(delim, prevPos);
        }

        if (pos == std::string::npos) {
            if(prevPos != text.size())
                vec.push_back(text.substr(prevPos));
            return vec;
        }

        vec.push_back(text.substr(prevPos, pos - prevPos));
        prevPos = pos + 1;
    }
}

Example without compress:

std::string s = "  1.2  foo@foo . ";
auto res = split(s, ".@ ", false);
    for(auto i : res)
        std::cout << "string {" << i << "}" << std::endl;

Output:

string {}
string {}
string {1}
string {2}
string {}
string {foo}
string {foo}
string {}
string {}

With compress split(s, ".@ ", true);

string {1}
string {2}
string {foo}
string {foo}

Answer 11

Here's a function that will split up a string into a vector but it doesn't include empty strings in the output vector.

vector<string> split(string str, string token) {
    vector<string> result;
    while (str.size()) {
        int index = str.find(token);
        string substr;
        if ((substr = str.substr(0, index)) == "") {
            str = str.substr(index + token.size());
        } else if (index != string::npos) {
            result.push_back(substr);
            str = str.substr(index + token.size());
        } else {
            result.push_back(str);
            str = "";
        }
    }
    return result;
}

Note: The above was adapted from this answer.

Answer 12

Usage

void test() {
    string a = "hello : world : ok : fine";
    auto r = split(a, " : ", 2);
    for (auto e: r) {
        cout << e << endl;
    }
}


static inline std::vector<std::string> split(const std::string &str, const std::string &delimiter = " ", const int max_elements = 0) {
    std::vector<std::string> tokens;
    std::string::size_type start_index = 0;
    while (true) {
        std::string::size_type next_index = str.find(delimiter, start_index);
        if (next_index == std::string::npos) {
            tokens.push_back(str.substr(start_index));
            break;
        } else {
            tokens.push_back(str.substr(start_index, next_index - start_index));
            start_index = next_index + delimiter.length();
        }
        if (max_elements > 0 && tokens.size() == max_elements - 1) {
            tokens.push_back(str.substr(start_index));
            break;
        }
    }

    return tokens;
}