C++ split string by line

Question

I need to split string by line. I used to do in the following way:

int doSegment(char *sentence, int segNum)
{
assert(pSegmenter != NULL);
Logger &log =          


        

Answer 1

#include <iostream>
#include <string>
#include <regex>
#include <algorithm>
#include <iterator>
    
using namespace std;


vector<string> splitter(string in_pattern, string& content){
    vector<string> split_content;

    regex pattern(in_pattern);
    copy( sregex_token_iterator(content.begin(), content.end(), pattern, -1),
    sregex_token_iterator(),back_inserter(split_content));  
    return split_content;
}
    
int main()
{   

    string sentence = "This is the first line\n";
    sentence += "This is the second line\n";
    sentence += "This is the third line\n";

    vector<string> lines = splitter(R"(\n)", sentence);

    for (string line: lines){cout << line << endl;}

}   

1. We have a string with multiple lines
2. we split those into an array (vector)
3. We print out those elements in a for loop

Answer 2

I'd like to use std::getline or std::string::find to go through the string. below code demonstrates getline function

int doSegment(char *sentence)
{
  std::stringstream ss(sentence);
  std::string to;

  if (sentence != NULL)
  {
    while(std::getline(ss,to,'\n')){
      cout << to <<endl;
    }
  }

return 0;
}

Answer 3

You can call std::string::find in a loop and the use std::string::substr.

std::vector<std::string> split_string(const std::string& str,
                                      const std::string& delimiter)
{
    std::vector<std::string> strings;

    std::string::size_type pos = 0;
    std::string::size_type prev = 0;
    while ((pos = str.find(delimiter, prev)) != std::string::npos)
    {
        strings.push_back(str.substr(prev, pos - prev));
        prev = pos + 1;
    }

    // To get the last substring (or only, if delimiter is not found)
    strings.push_back(str.substr(prev));

    return strings;
}

See example here.

Answer 4

std::vector<std::string> split_string_by_newline(const std::string& str)
{
    auto result = std::vector<std::string>{};
    auto ss = std::stringstream{str};

    for (std::string line; std::getline(ss, line, '\n');)
        result.push_back(line);

    return result;
}

Answer 5

This fairly inefficient way just loops through the string until it encounters an \n newline escape character. It then creates a substring and adds it to a vector.

std::vector<std::string> Loader::StringToLines(std::string string)
{
    std::vector<std::string> result;
    std::string temp;
    int markbegin = 0;
    int markend = 0;

    for (int i = 0; i < string.length(); ++i) {     
        if (string[i] == '\n') {
            markend = i;
            result.push_back(string.substr(markbegin, markend - markbegin));
            markbegin = (i + 1);
        }
    }
    return result;
}