Remove extra white spaces in C++

Question

I tried to write a script that removes extra white spaces but I didn\'t manage to finish it.

Basically I want to transform abc sssd g g sdg gg gf into

Answer 1

You can use std::unique which reduces adjacent duplicates to a single instance according to how you define what makes two elements equal is.

Here I have defined elements as equal if they are both whitespace characters:

inline std::string& remove_extra_ws_mute(std::string& s)
{
    s.erase(std::unique(std::begin(s), std::end(s), [](unsigned char a, unsigned char b){
        return std::isspace(a) && std::isspace(b);
    }), std::end(s));

    return s;
}

inline std::string remove_extra_ws_copy(std::string s)
{
    return remove_extra_ws_mute(s);
}

std::unique moves the duplicates to the end of the string and returns an iterator to the beginning of them so they can be erased.

Additionally, if you must work with low level strings then you can still use std::unique on the pointers:

char* remove_extra_ws(char const* s)
{
    std::size_t len = std::strlen(s);

    char* buf = new char[len + 1];
    std::strcpy(buf, s);

    // Note that std::unique will also retain the null terminator
    // in its correct position at the end of the valid portion
    // of the string    
    std::unique(buf, buf + len + 1, [](unsigned char a, unsigned char b){
        return (a && std::isspace(a)) && (b && std::isspace(b));
    });

    return buf;
}