c++ - 如何在c ++中删除字符串中的某些字符？

Question

For example, if i'm taking in the string below.

"{{((A+b)-xyz)addf}sss}";

I would like to ignore all characters that aren't a parenthesis or curly bracket, resulting.

"{{(())}}"

What method would be most efficient to do.

Answer 1

You didn't specify how exactly you obtain the string, but considering:

std::string str = "{{((A+b)-xyz)addf}sss}";

You could use the erase-remove idiom. We specify a custom deleter, which will be a function (actually a lambda - a functor) that will check for a character not being a curly bracket or a parenthesis.

auto deleter = [](const char c){
    return c != '(' && c != ')' && c != '{' && c != '}';
};

Then we use erase-remove idiom:

str.erase(std::remove_if(str.begin(), str.end(), deleter), str.end());

This will result in the original str turning into: {{(())}} .