I want to join a vector<string> into a single string, separated by spaces. For example,
sample
string
for
this
example
should become "sample string for this example".
What is the simplest way to do this?
#include <iterator>
#include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
std::vector<std::string> v;
...
std::stringstream ss;
std::copy(v.begin(), v.end(), std::ostream_iterator<std::string>(ss, " "));
std::string result = ss.str();
if (!result.empty()) {
result.resize(result.length() - 1); // trim trailing space
}
std::cout << result << std::endl;
boost::join
Related
I want to remove a character ('#') from a string,
I tried to check if the string has '#' with the find function, which it does, then erase this with the erase function.
For some reason I get a run time error that says I have no memory.
Error: std::out_of_range at memory location 0x003BF3B4
#include <iostream>
#include <algorithm>
#include <string>
int main()
{
std::string str = "Hello World#";
if (str.find('#')) {
str.erase('#');
}
return 0;
}
The excepted output is: "Hello World"
Try something like this:
#include <algorithm>
str.erase(std::remove(str.begin(), str.end(), '#'), str.end());
#include <iostream>
#include <string>
#include <algorithm>
int main()
{
std::string s = "Hello World#";
char c = '#';
/* Removing character c from s */
s.erase(std::remove(s.begin(), s.end(), c), s.end());
std::cout << "\nString after removing the character "
<< c << " : " << s;
}
If you want to delete all '#' from the string:
std::string str = "Hello World#";
std::size_t pos = str.find('#');
while(pos != std::string::npos)
{
str.erase(pos, 1); //<- edited here
pos = str.find('#');
}
cout << str;
I have some string :
testing testing
test2test2
these lines are devided by CRLF. I saw that there are : 0d0a0d0a deviding them.
How can I split it using this information?
I wanted to use str.find(CRLF-DELIMITER) but can't semm to figure how
editing :
I already used str.find("textDelimiter"), but now I need it to look for hexa and not search for a string "0d0a0d0a"
Use boost::split to do that. Please also take a look at Boost.Tokenizer.
Here is another way of doing it using regex:
using std::endl;
using std::cout;
using std::string;
using std::vector;
using boost::algorithm::split_regex;
int main()
{
vector<string> res;
string input = "test1\r\ntest2\r\ntest3";
split_regex(res, input, boost::regex("(\r\n)+"));
for (auto& tok : res)
{
std::cout << "Token: " << tok << std::endl;
}
return 0;
}
Here is the way of doing it without Boost:
#include <string>
#include <sstream>
#include <istream>
#include <vector>
#include <iostream>
int main()
{
std::string strlist("line1\r\nLine2\r\nLine3\r\n");
std::istringstream MyStream(strlist);
std::vector<std::string> v;
std::string s;
while (std::getline(MyStream, s))
{
v.push_back(s);
std::cout << s << std::endl;
}
return 0;
}
ostringstream ss;
ss << "(1,2)\n" << "(1,3)\n" << "(1,4)\n" ;
cout << ss.str();
should print the following:
(1,2)
(1,3)
(1,4)
How could i reverse the output by line so that it prints:
(1,4)
(1,3)
(1,2)
You could use a custom std::streambuf which internally keeps a stack of std::strings and puts them together upon using a str() member. For example:
#include <iostream>
#include <numeric>
#include <streambuf>
#include <string>
#include <vector>
class stackbuf
: public std::streambuf
{
std::vector<std::string> d_lines;
int overflow(int c) {
if (c != std::char_traits<char>::eof()) {
this->d_lines.back().push_back(c);
if (c == '\n') {
this->d_lines.push_back(std::string());
}
}
return std::char_traits<char>::not_eof(c);
}
public:
stackbuf(): d_lines(1) {}
std::string str() const {
return std::accumulate(this->d_lines.rbegin(),
this->d_lines.rend(),
std::string());
}
};
int main()
{
stackbuf sbuf;
std::ostream out(&sbuf);
out << "(1, 2)\n(1, 3)\n(1, 4)\n";
std::cout << sbuf.str();
}
For a real-world application you should, obviously, set up a buffer in the stream buffer to improve the performance. You may also want to create a custom stream directly initializing the stream's stream buffer.
Using your original code with C++98:
ostringstream ss;
ss << "(1,2)\n" << "(1,3)\n" << "(1,4)\n" ;
cout << ss.str();
//assign a string to the contents of the ostringstream:
string rawlines = ss.str();
//now create an input stringstream with the value of the rawlines
istringstream iss(rawlines);
string temp;//just a temporary object used for storage
vector<string> lines;//this is where your lines will be held
//now iterate over the stream and store the contents into the vector `lines`:
while(getline(iss, temp)) {
lines.push_back(temp);
}
//now reverse the contents:
reverse(lines.begin(), lines.end());
//see what's inside:
for (vector<string>::const_iterator it = lines.begin(); it != lines.end(); ++it) {
cout << *it << endl;
}
This will print:
(1,4)
(1,3)
(1,2)
As desired
NOTE: This strips the newlines from the the original string.
And, this requires:
//for `getline`:
#include <cstdlib>
//for `reverse`:
#include <algorithm>
//for `string`:
#include <string>
//for `vector`:
#include <vector>
You can use reverse iterators:
std::ostringstream ss{ "(1,2)\n(1,3)\n(1,4)\n" };
std::string str = ss.str();
std::copy( str.rbegin(), str.rend(),
std::ostream_iterator<std::string>{std::cout, "\n"} );
This code will require:
#include <iostream>
#include <algorithm>
#include <iterator>
#include <string>
#include <sstream>
and basic C++11 support.
This would be the classic way, best leveraging the standard C++ library.
#include <iostream>
#include <sstream>
#include <stack>
#include <string>
using namespace std;
int main(int argv, char* arv[])
{
ostringstream oss;
oss << "(1,2)\n" << "(1,3)\n" << "(1,4)\n" ;
cout << oss.str() << "----------\n";
// Reverse lines
// Fill an istringstream with buffer contents of the ostringstream
istringstream iss(oss.str());
stack<string> stk;
while (iss) {
string s;
if (!getline(iss, s)) break; // Read a line
s += '\n'; // Put back newline stripped by readline
stk.push(s); // Push line to stack
}
oss.clear(); // Clear state of the ostringstream
oss.str(""); // Clear contents of the ostringstream for reuse
while (!stk.empty()) {
string s;
s = stk.top(); // Get top of stack
oss << s; // Output it to the ostringstream
stk.pop(); // Pop and throw away top of stack
}
cout << oss.str();
return 0;
}
I'm looking for the best way to remove the first word from a std::string. This is what I have but I feel that this is overcompilicating things. What's the best and shortest way to do this? Thanks.
#include <string>
#include <iostream>
#include <sstream>
int main()
{
std::string str{"Where is everybody?"};
std::string first;
if (std::stringstream{str} >> first)
{
str.erase(str.begin(), str.begin() + first.size());
}
std::cout << str; // " is everybody?"
}
minor tweak, that leverages IO streams for the second half too :)
#include <string>
#include <iostream>
#include <sstream>
int main()
{
std::string str{"Where is everybody?"};
std::string first;
std::istringstream iss{str};
iss >> first;
std::ostringstream oss;
oss << iss.rdbuf();
std::cout << oss.str(); // " is everybody?"
}
You can do it without a stream: skip the initial spaces, locate the first space after that, walk to the next non-space, and use substr to get the rest of the string:
int i = 0;
while (isblank(str[i])) i++;
while (!isblank(str[i])) i++;
while (isblank(str[i])) i++;
str = str.substr(i);
Here is a demo on ideone.
Here is a solution using c++11's regex
#include <iostream>
#include <string>
#include <regex>
#include <iterator>
int main ()
{
std::string s ("there is a subsequence in the string\n");
std::regex e ("(\\s*)(\\w*)(.*)");
std::cout << std::regex_replace (s,e,"$1$3");
return 0;
}
You could try using string::substr() and string::find_first_of().
The best I can come up with is:
#include <boost/algorithm/string/replace.hpp>
#include <boost/regex.hpp>
#include <iostream>
using namespace std;
int main() {
string dog = "scooby-doo";
boost::regex pattern("(\\w+)-doo");
boost::smatch groups;
if (boost::regex_match(dog, groups, pattern))
boost::replace_all(dog, string(groups[1]), "scrappy");
cout << dog << endl;
}
with output:
scrappy-doo
.. is there a simpler way of doing this, that doesn't involve doing two distinct searches? Maybe with the new C++11 stuff (although I'm not sure that it's compatible with gcc atm?)
std::regex_replace should do the trick. The provided example is pretty close to your problem, even to the point of showing how to shove the answer straight into cout if you want. Pasted here for posterity:
#include <iostream>
#include <iterator>
#include <regex>
#include <string>
int main()
{
std::string text = "Quick brown fox";
std::regex vowel_re("a|e|i|o|u");
// write the results to an output iterator
std::regex_replace(std::ostreambuf_iterator<char>(std::cout),
text.begin(), text.end(), vowel_re, "*");
// construct a string holding the results
std::cout << '\n' << std::regex_replace(text, vowel_re, "[$&]") << '\n';
}