Count number of occurence of a node in a trie data structure

Question

I have a trie where each node is an object TrieNode like this:

public char content; 
public double count;
public LinkedList<TrieNode> childList; 

I had to count the occurrence of a specific char in the trie. I think to sum the count field of nodes that have content = char I'm looking for.

So this is what I've done:

int occ = occurrencesOfChar(0, root, c);

public int occurrencesOfChar(int occ, TrieNode node, char c) {
    for(TrieNode child : node.childList) {
        if(child.content == c) { 
            occ += child.count; 
        }
        occ += occurrencesOfChar(occ, child, c);
    }
    return occ;
}

But the result is overestimated, returns more occurences than those that actually are. Why?

Answer 1

You're adding to occ multiple times because you're passing it as a parameter. You should use a local variable:

public int occurrencesOfChar(TrieNode node, char c) {
    int occ = 0;
    for(TrieNode child : node.childList) {
        if(child.content == c) { 
            occ += child.count; 
        }
        occ += occurrencesOfChar(child, c);
    }
    return occ;
}