如何有效地从一定长度的字符串向量中删除单词

Question

I am currently trying to work with a vector of strings, and need to be able to efficiently remove elements that are not of a certain string length.

I was thinking about doing something like vector.erase(remove_if(etc)) , however I can't use lambdas due to using C++98, and if I were to create a predicate it would need parameters because the length is a variable and can change based on user input.

Can anyone provide a basic solution to this with these restrictions?

Answer 1

It's not like in C++03 you didn't have functors, they were just 10x more awkward to use...

// important: outside from any function
// (local types weren't allowed as template parameters) 
struct size_mismatcher {
    size_t size;
    size_mismatcher(size_t size) : size(size) {}
    bool operator()(const std::string& s) { return s.size() != size; }
};

// in your function:
vec.erase(std::remove_if(vec.begin(), vec.end(),
                         size_mismatcher(target_size)),
          vec.end());

Or just do it the classic way:

size_t wp = 0;
for(size_t rp = 0, n = vec.size(); rp != n; ++rp) {
    if(vec[rp].size() == target_size) {
        vec[wp] = vec[rp];
        ++wp;
    }
}
vec.resize(wp);