How to split a space separated string into multiple strings in C++?

c++ string stream

31,504

Solution 1

You are asking how to split a string. Boost has a helpful utility boost::split()

http://www.boost.org/doc/libs/1_48_0/doc/html/string_algo/usage.html#id3115768

Here's an example that puts the resulting words into a vector:

#include <boost/algorithm/string.hpp>
std::vector<std::string> strs;
boost::split(strs, "string to split", boost::is_any_of("\t "));

Solution 2

Code in c++
#include<sstream>
#include<vector>
using namespace std;    
string diskNames="vbbc anmnsa mansdmns";
string temp;
vector <string> cds;
stringstream s (diskNames);
while(s>> temp)
cds.push_back(temp);

Solution 3

Use stream iterators and a standard function:

static int myfunc(std::string const& stringInput)
{
    std::stringstream ss(stringInput);

    std::for_each(std::istream_iterator<std::string>(ss),
                  std::istream_iterator<std::string>(),
                  [&counters](std::string const& word) { ++counters[word];}
                 )
    ...
}

If you don't have lambda then:

struct Helper
{
     void operator()(std::string const& word) const {++counters[word];}
     Helper(CounterType& c) : counters(c) {}
     CounterType& counters;
};

static int myfunc(std::string const& stringInput)
{
    std::stringstream ss(stringInput);

    std::for_each(std::istream_iterator<std::string>(ss),
                  std::istream_iterator<std::string>(),
                  Helper(counters)
                 )
    ...
}

31,504

Author by

Qiang Xu

Updated on July 09, 2022

Comments

Qiang Xu almost 2 years
Somewhat my code looks like below:
```
static int myfunc(const string& stringInput)
{
    string word;
    stringstream ss;

    ss << stringInput;
    while(ss >> word)
    {
        ++counters[word];
    }
    ...
}
```
The purpose here is to get an input string (separated by white space ' ') into the string variable word, but the code here seems to have a lot of overhead -- convert the input string to a string stream and read from the string stream into the target string.

Is there a more elegant way to accomplish the same purpose?
Qiang Xu over 12 years

Yep, this saves a little bit. But the basic idea is still the same: construct a stringstream, and read from this stream. Could we not use the streamstream at all? And still read the space separated string into word?
Qiang Xu over 12 years

Thanks, but I intend to discard the use of stream if possible.
Qiang Xu over 12 years

Thank you, alex. Yeah, this is what I want. But I am not sure whether my g++ compiler comes with boost library, how to check the existence of boost? Btw, any additional -l command to use in compiling the source code? If there is no boost available, is there a similar utility function in STL?
alex tingle over 12 years

Sorry for the ninja edit there. I mistook your question, at first.
Qiang Xu over 12 years

By the way, alex. Just find another split()'s implementation in the classical "Accelerated C++" by Andrew Koenig. The implementation is provided in Section 5.6 (Taking strings apart) of Chapter 5.
Qiang Xu over 12 years

Thank you, Loki. Your code looks awesome. Still, I prefer a way not to involve stream. :-)
Qiang Xu over 12 years

Thank you, Petro. Your split routine is quite similar to Andrew Koenig's in his "Accelerated C++". Both are nice functions.
ildjarn over 12 years

@Qiang : You tagged your own question stream but you're trying to avoid streams? That's slightly misleading.