此正则表达式在C ++中不起作用 [英] This regex doesn't work in c++

问题描述

应该匹配 abababab ，因为 ab 连续重复两次以上，但是代码不打印任何输出。
在C ++中使用正则表达式还有其他技巧吗？

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++.

我尝试过使用其他语言，而且效果很好。

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;
}

推荐答案

您的问题是您的反斜杠是转义字符串中的 1。您需要通知std :: regex将其视为。您可以通过使用原始字符串R（（。+）\1\1 +）或转义斜线来完成此操作，如下所示：

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;
}

哪个会产生输出

abababab ab 

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