Splitting a string without losing the separator

Question

I took this code for string split here: string split

char sep = ' ';
std::string s="1 This is an exampl";

for(size_t p=0, q=0; p!=s.npos; p=q)
std::cout << s.substr(p+(p!=0), (q=s.find(sep, p+1))-p-(p!=0)) << std::endl;

The code works ok and the output is:

1
This
is
an
exampl

If I change the separator from ' ' to 'e', the output is:

1 This is an
xampl

The 'e' in exampl is lost. How can I split the string using the same code but not losing the letter used as the separator?

Answer 1

I suggest splitting the string with a simple \b(?=e) regex (matching an e only if it is not preceded with a letter, digit or underscore):

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

int main() {
    std::vector<std::string> strings;
    std::string s = "1 This is an exampl";
    std::regex re("\\b(?=e)");
    std::regex_token_iterator<std::string::iterator> it(s.begin(), s.end(), re, -1);
    decltype(it) end{};
    while (it != end){
        strings.push_back(*it++);
        std::cout << strings[strings.size()-1] << std::endl; // DEMO!
    }
    return 0;
}

See the C++ demo.