CODEWITHSUNDEEP
c++regex
user2798694
user2798694

Reputation: 1033

This regex doesn't work in c++

It is supposed to match "abababab" since "ab" is repeated more than two times consecutively but the code isn't printing any output. Is there some other trick in using regex in C++.

I tried with other languages and it works just fine.

#include<bits/stdc++.h>

int main(){

  std::string s ("xaxababababaxax");
  std::smatch m;
  std::regex e ("(.+)\1\1+");   

   while (std::regex_search (s,m,e)) {
    for (auto x:m) std::cout << x << " ";
    std::cout << std::endl;
    s = m.suffix().str();
  }

  return 0;
}

Upvotes: 4

Views: 2558

Answers (1)

Spacemoose
Spacemoose

Reputation: 4016

Your problem is your backslashes are escaping the '1''s in your string. You need to inform std::regex to treat them as '\' 's. You can do this by using a raw string R"((.+)\1\1+)", or by escaping the slashes, as shown here:

#include <regex>
#include <string>
#include <iostream>


int main(){

  std::string s ("xaxababababaxax");
  std::smatch m;
  std::regex e ("(.+)\\1\\1+");

   while (std::regex_search (s,m,e)) {
    for (auto x:m) std::cout << x << " ";
    std::cout << std::endl;
    s = m.suffix().str();
  }

  return 0;
}

Which produces the output

abababab ab

Upvotes: 7

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