如何使用 c++ 从字符串中删除前后的撇号

Question

I ran into a little trouble with removing the first and last apostrophe from string. I have a vector of string and some of them have apostrophe either at from or back of string. For example, I have {'cause, 'til, holdin', don't} I want output like this {cause, til, holdin, don't} How do I do this?

Answer 1

You remove characters from strings with the .erase() member function. Example:

#include <iostream>
#include <string>
#include <vector>

void trim_inplace(std::string &s, char c) {
  if (s.size() >= 2) {
    auto it = s.begin();
    if (*it == c) {
      s.erase(it);
    }
    it = s.end() - 1;
    if (*it == c) {
      s.erase(it);
    }
  }
}

int main() {
  std::vector<std::string> foo{"'cause", "'til", "holdin'", "don't"};
  for (auto &s : foo) {
    std::cout << s << " -> ";
    trim_inplace(s, '\'');
    std::cout << s << '\n';
  }
  return 0;
}

Answer 2

I came up with following implementations, which covers the empty input scenario without invoking any undefined behaviour.

#include <vector>
#include <string>
#include <iostream>
#include <algorithm>

std::vector<std::string> contents = {"'cause", "'til", "holdin'", "don't", ""};

void impl1() {
    for(auto & content:contents){
        if(!content.empty() && (*content.begin()) == '\''){
            content.erase(content.begin());
        }

        if(!content.empty() && content.back() == '\''){
            content.pop_back();
        }

        std::cout << content << " " << std::endl;
    }
}

void impl2(){
    auto erase_if = [](auto& container, auto&& itr, auto val){
        if(!(itr == std::end(container)) && ((*itr) == val)){
            container.erase(itr);
        }  
    };   
    for(auto & content: contents){
        erase_if(content, content.begin(), '\'');
        erase_if(content, std::string::iterator{&content.back()}, '\'');

        // print trimmed output
        std::cout << content << " " << std::endl;
    }
}


int main(void){
    //impl1();
    impl2();
    return 0;
}