Strings :: Removing Parenthesis and characters inside of it-CodePudding

This is my first question im sorry if I broke any rules doing so. Anyways my question is about strings. How do I delete parenthesis as well as the text inside of that in a string? for example.. I have a string "example (stuff) example". I want to be able to remove the parenthesis and the characters inside of it every time, whether its like this "(stuff) example example" or this "example example (stuff)". I am also new to c and am using replit as my ide and it doesnt contain an autofill feautre so I dont know what functions im working with making this task hard. If you could also point me in a direction about std::methods please let me know.

Im really new to programming and have usually received help when writing code and am now doing independent work while on break from college.

#include <string>

std::string remove_parentheses(const std::string &str) {
    int i = 0;
    while(i < str.length()) {
        if(str[i] == '(' || str[i] == ')' ) {
            str.erase(i,1);
        } else{i  } 
    }
    return str; // your code here
}

int main() {
    std::string str = "Computer systems";
    remove_parentheses(str);
    return 0;
}

it says..

error: no matching member function for call to 'erase' str.erase(i,1);

input "computer (computer systems) systems"
output "computer systems"

is this not the right way to erase? I cant find the list of functions for strings or std:: functions. thanks for the help!

CodePudding user response：

You can't erase things from a const reference. The const modifier is designed specifically to prohibit you from modifying the referent. If you want to modify it in-place, take a non-const reference.

void remove_parentheses(std::string &str)

If you want to make a new string with the modifications intact, take the string by value (incurring a copy when you call the function) and return the new string.

std::string remove_parentheses(std::string str)

CodePudding user response：

Addendum to Silvio Mayolo's answer, but I would strongly recommend outputting a new string as opposed to modifying the existing string in-place. We can use a variable to track levels of nested parentheses, and a std::ostringstream to efficiently build up a new string minus the parens and their contents.

std::string remove_parentheses(const std::string &str) {
    int paren_level = 0;
    std::ostringstream ss;

    for (auto ch : str) {
        if (ch == '(') {
            paren_level  ;
        }
        else if (ch == ')' && paren_level > 0) {
            paren_level--;
        }
        else if (paren_level == 0) {
            ss << ch;
        }
    }

    return ss.str();
}

CodePudding user response：

You can also start getting used to STL algorithms. Since C 20, you can use std::string::erase_if, which will basically:

Walk every character of a string, and erase those that satisfy a condition (the size of the modified string is updated accordingly).
The condition would be: I've found a close paren, or I have an open paren yet to close. As already explained in @Chris's answer.
We could work on a copy of the input string, and return that copy.

[Demo]

#include <iostream>  // cout
#include <string>

std::string remove_parentheses(std::string str) {
    int no_of_open_parens{ 0 };
    std::erase_if(str,
        [&no_of_open_parens](char c) {
            if (c == '(') {
                no_of_open_parens  ;
            } else if (c == ')' and no_of_open_parens > 0) {
                no_of_open_parens--;
            }
            return c == ')' or no_of_open_parens > 0;
        }
    );
    return str;
}

int main() {
    std::string in_str = "Computer (computer systems) systems";
    auto out_str = remove_parentheses(in_str);
    std::cout << out_str << "\n";
}

// Outputs: Computer  systems