Finding longest word in a digital tree with recursion

Question

I have a simple digital tree defined as below:

class DTN {
  public:
    DTN () :
      is_word(false), word_to_here(""), children()
    {}
    DTN (bool iw, std::string wth) :
      is_word(iw), word_to_here(wth), children()
    {}
    bool                     is_word;
    std::string              word_to_here;
    Map<char,DTN>  children;
};

I am having problem to define a function called longest_word (const DTN& dtn) which is suppose to return the longest word in the digital tree with iterator and recursion, shown as follow:

std::string longest_word (const DTN& dtn) {
    std::string lw = dtn.word_to_here;
    for(auto s:dtn.children){
        if(s.second.is_word && lw.length()<s.second.word_to_here.length()){
            lw = longest_word(s.second);
        }
        longest_word(s.second);
    }
    return lw;
}

Assume we have three words in a digital tree DTN: (ante, anteater, anthebellum), and calling the longest_word(DTN) will give me an empty string "" instead of "anthebellum". Can someone please point out what I did wrong in the longest_word function? With actual code will be appreciated because my English is not good, codes are easier for me to understand. Thanks in advance.

Answer 1

The algorithm for longest_word is completely wrong. You should inspect all children longest_words and return the one which is longer. You cannot return before the loop on children is complete. Notice that your algorithm will always return on first children. I don't even understand why you check for a complete word there...

I could try to write the correct code but I feel it is not useful to you. My suggestion is to get back to simplest algorithms like finding the maximum number in a list of integers.