Question

The code function that I’m specifically talking about is getCount(). There are several other functions that I haven’t included here (such as finding the height of this binary tree and the total node count) which work just fine, with correct results. getCount() on the other hand produces segmentation fault except for the first node (the top, first node of the tree). Any ideas?

#include <string> 
#include <algorithm>
#include <iostream>

class Word {
    public:
        std::string keyval;
        long long count;
        Word() {
            keyval = "";
            count = 0;
        }
        Word(std::string S) {
            keyval = S;
            count = 1;
        }
};

class WordBST {
    public:
        Word node;
        WordBST* left_child;
        WordBST* right_child;
        WordBST(std::string key);        
        void add(std::string key){
            if (key == node.keyval){
                node.count++;
            }
            else if (key < node.keyval){
                if (left_child == NULL){
                    left_child = new WordBST(key);
                }else {
                    left_child->add(key);
                }
            }else {
                if (right_child == NULL){
                    right_child = new WordBST(key);
                }else {
                    right_child->add(key);
                }
            }
        }
        long long getCount(std::string key){
            if (key == node.keyval){
                return (node.count);
            }
            else if (key < node.keyval){
                left_child->getCount(key);
            }else if(key > node.keyval){
                right_child->getCount(key);
            }else return 0;
            /*else {
                if (key < node.keyval){
                    left_child->getCount(key);
                }else{
                    right_child->getCount(key);
                }
            }*/
        }
};

WordBST::WordBST(std::string key) {
    node = Word(key);
    left_child = NULL;
    right_child = NULL;
}

Answer 1

This is because you let your code run off the end without hitting a return statement.

long long getCount(std::string key){
    if (key == node.keyval){
        return (node.count);
    } else if (left_child && key < node.keyval){
        return left_child->getCount(key); // Added return
    } else if(right_child && key > node.keyval){
        return right_child->getCount(key); // Added return
    }
    return 0;
}

You also need to add null checks in more than one place throughout the code. Your add method has them, but your getCount does not.