How would I get the last part of a URL?
Say the variable url is https://somewhere.com/stuff/hello.
How would I get hello from this?
Using rfind and substr
Maybe with
#include <iostream>
#include <string>
int main() {
std::string url{"https://somewhere.com/stuff/hello"};
std::cout << url.substr(url.rfind('/')+1);
return 0;
}
But only, if you have a / in front of the last part
#include <iostream>
#include <string>
int main() {
const std::string url("https://somewhere.com/stuff/hello");
const std::size_t indexLastSeparator = url.find_last_of("/");
if (indexLastSeparator != std::string::npos)
{
const std::string lastPartUrl = url.substr(indexLastSeparator+1); // +1 to not keep /
std::cout << lastPartUrl << '\n'; // print "hello"
}
}
With find_last_of() and substr()
references :
https://en.cppreference.com/w/cpp/string/basic_string/find_last_of
https://en.cppreference.com/w/cpp/string/basic_string/substr
Related
We have a char. We need to replace all ab characters from our char with the letter c.
Example we have :
abracadabra
the output will be :
cracadcra
I tried to use replace() function from C++, but no success.
#include <iostream>
#include <cstring>
using namespace std;
int main()
{
string test;
cin>>test;
for(int i=0;i<(strlen(test)-1);i++)
{
if((test[i]=='a')&&(test[i+1]=='b')){
test.replace( test[i], 'c' );
test.replace( test[i+1] , ' ' );
}
}
cout << test << endl;
return 0;
}enter code here
You can use C++11 regex:
#include <iostream>
#include <regex>
#include <string>
int main() {
std::string str = "abracadabra";
std::regex r("ab");
std::cout << std::regex_replace(str, r, "c") << "\n"; // cracadcra
}
Problem:
That is not the syntax of std::string::replace.
Solution:
As is mentioned here the syntax is std::string::replace(size_t pos, size_t len, const string& str). Do test.replace(i, 2, "c" ) instead of test.replace(test[i],'c').
Or use regular expressions as dtell pointed.
Adittional information:
using namespace std; is considered a bad practice (More info here).
You should use std::string::size instead of strlen when you're working with std::string.
To work with std::string you should use #include <string> instead of #include <cstring>.
Full code:
#include <iostream>
int main()
{
std::string test;
std::cin >> test;
for(unsigned int i = 0; i < test.size() - 1; i++)
{
if((test[i]=='a') && (test[i+1]=='b'))
{
test.replace(i, 2, "c" );
}
}
std::cout << test << std::endl;
return 0;
}
The simplest thing you can do by using the standard library is first to find ab and then replace it. The example code I wrote is finding string ab unless there is None in the string and replacing it with c.
#include <iostream>
#include <string>
int main()
{
std::string s = "abracadabra";
int pos = -1;
while ((pos = s.find("ab")) != -1)//finding the position of ab
s.replace(pos, sizeof("ab") - 1, "c");//replace ab with c
std::cout << s << std::endl;
return 0;
}
//OUTPUT
cracadcra
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;
How can I get a substring of a std::wstring which includes some non-ASCII characters?
The following code does not output anything:
(The text is an Arabic word contains 4 characters where each character has two bytes, plus the word "Hello")
#include <iostream>
#include <string>
using namespace std;
int main()
{
wstring s = L"سلام hello";
wcout << s.substr(0,3) << endl;
wcout << s.substr(4,5) << endl;
return 0;
}
This should work: live on Coliru
#include <iostream>
#include <string>
#include <boost/regex/pending/unicode_iterator.hpp>
using namespace std;
template <typename C>
std::string to_utf8(C const& in)
{
std::string result;
auto out = std::back_inserter(result);
auto utf8out = boost::utf8_output_iterator<decltype(out)>(out);
std::copy(begin(in), end(in), utf8out);
return result;
}
int main()
{
wstring s = L"سلام hello";
auto first = s.substr(0,3);
auto second = s.substr(4,5);
cout << to_utf8(first) << endl;
cout << to_utf8(second) << endl;
}
Prints
سلا
hell
Frankly though, I think your substring calls are making weird assumptions. Let me suggest a fix for that in a minute:
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().
How can I get :
connect
100
username
example
from this string:
ngg://connect>100/username>example/
Using std::string::find with arguments "/" and ">" and std::string::substr with the found indexes.
This is a good start.
Adding an answer with strtok for the sake of diversity:
char str[] = "ngg://connect>100/username>example/";
char *s = strtok(str, ">/");
std::vector<std::string> tokens;
while (s = strtok(NULL, ">/"))
tokens.push_back(std::string(s));
This will split the string str into the desired tokens (discarding the first ngg:, like in the question).
Here's a working example of this code.
A possibility is boost::split():
#include <iostream>
#include <vector>
#include <string>
#include <boost/algorithm/string.hpp>
#include <boost/algorithm/string/split.hpp>
int main()
{
std::vector<std::string> tokens;
std::string s("ngg://connect>100/username>example/");
boost::split(tokens, s, boost::is_any_of("/>"));
// "connect" == tokens[2]
// "100" == tokens[3]
// "username" == tokens[4]
// "example" == tokens[5]
return 0;
}
ngg://connect>100/username>example/
If this format is fixed, then you can use std::sscanf as:
#include <iostream>
#include <cstdio>
int main()
{
char const *input = "ngg://connect>100/username>example/";
char const *input_format = "ngg://%[^>]>%d/%[^>]>%[^/]";
char connect[100], user[100], str[100]; //assuming max size is 100
int num;
if ( std::sscanf(input, input_format, connect, &num, user, str) != 4 )
{
std::cerr<<"error - number of tokens read must be equal to 4";
return 0;
}
std::cout << connect <<std::endl;
std::cout << num <<std::endl;
std::cout << user <<std::endl;
std::cout << str <<std::endl;
}
Output (online demo):
connect
100
username
example