How Can I Efficiently Remove Spaces from C Strings?

Efficient Space Removal from C Strings

Removing spaces from C strings is a common task for string manipulation. While it's possible to iterate through characters manually, there's a more efficient approach.

The preferred method involves the powerful standard library algorithm remove_if and the isspace predicate. remove_if eliminates elements from a sequence based on a specified condition, while isspace checks for whitespace characters.

To utilize this, you can call:

remove_if(str.begin(), str.end(), isspace);

This operation alone doesn't alter the string's length but rearranges the elements accordingly. To adjust the length, we use string::erase:

str.erase(remove_if(str.begin(), str.end(), isspace), str.end());

remove_if avoids multiple copies of data, making it highly efficient. Here's a simplified implementation:

template<typename T, typename P>
T remove_if(T beg, T end, P pred)
{
    T dest = beg;
    for (T itr = beg;itr != end; ++itr)
        if (!pred(*itr))
            *(dest++) = *itr;
    return dest;
}

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