Why I am getting "Unhandled Pointer exception"

[funprogrammer]

I am trying to implement trie structure for dictionary implementation in c++. I am running into unhandled pointer excpetion.

Strange thing is, I am not seeing any error when I put some breakpoint and run it, only when I run the debugger without any breakpoints I see the error.

Can someone please look at my code and tell me where I am going wrong?

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

using namespace std;

struct letter{
	char val;
	string word;
	letter *next[26];
};

class Dictionary{
	letter *root;
	void addWord(int pos,string str,letter ** leaf);
	bool findWord(int pos, string str,letter* leaf);
public:
	void addWord(string str);
	bool findWord(string str);
};

/*Private member functions*/
void Dictionary::addWord(string str){
	addWord(0,str, &root);
}

bool Dictionary::findWord(string str){
	return findWord(0,str,root);
}

/*Public member functions*/
/*Assuming input words are not case sensitive */
void Dictionary::addWord(int pos, string str, letter** leaf){
	if (*leaf == NULL){
		*leaf= new letter;
		(*leaf)->word="";
		(*leaf)->val = NULL;
		for (int i = 0; i < 26; i++){
			(*leaf)->next[i] = NULL;
		}
	}
	if (str.length() == pos){
		(*leaf)->word = str;
		return;
	}
	if ((*leaf)->next[(str[pos] - 'a')]==NULL){
		letter *temp = new letter;
		temp->val = str[pos];
		for (int i = 0; i < 26;i++){
			temp->next[i] = NULL;
		}
		temp->word = "";
		(*leaf)->next[(str[pos] - 'a')]=temp;
		addWord(pos+1,str,&(*leaf)->next[(str[pos]-'a')]);
	}
	else{
		addWord(pos+1,str,&((*leaf)->next[(str[pos]-'a')]));
	}
}

bool Dictionary::findWord(int pos,string str,letter* leaf){
	if (leaf == NULL){
		return false;
	}
	if (leaf->word.compare(str) == 0){
		return true;
	}
	else{
		if (leaf->val == str[pos]){
			return findWord(pos+1, str,leaf->next[(str[pos] - 'a')]);
		}
		else{
			if (leaf->next[str[pos] - 'a'] == NULL)
				return false;
			else{
				return findWord(pos+1,str,leaf->next[(str[pos]-'a')]);
			}
		}
	}
}


int main(){
	Dictionary d1;
	string temp;
	ifstream file;
	file.open("words.txt");
	while (!file.eof()){
       file >> temp;
       transform(temp.begin(),temp.end(),temp.begin(),tolower);
	   d1.addWord(temp);
	}
	cout << "Enter the word to be searched:" << endl;
	cin >> temp;
	cout << "The answer is " << d1.findWord(temp)<<endl;
	cin.ignore();
	getchar();
	return 0;
}

[cire]

I don't know why every node would have a word. Words are defined by traversal through the nodes of the trie. There is no need or reason to have the word additionally stored in a node. A simple boolean value would be enough to indicate whether the sequence is an actual word that has been inserted into the trie or merely a part of a larger word inserted.

The way you're reading the input file is wrong:

    while (file >> temp)
    {
        if (!temp.empty())
        {
            transform(temp.begin(), temp.end(), temp.begin(), tolower);
            d1.addWord(temp);
        }
    }

[ne555]

Initialize your variables.
Create a constructor for Dictionary where you set the value of root.

[funprogrammer]

Thanks @cire and @ne555.

@cire: I understand !temp.empty() part of it, what about while(!file.eof) and file>>temp. Isn't that same as what you added while(file>>temp)? Is there a difference?

[cire]

In my while loop we know the input extraction was successful before we attempt to do anything with it. In yours, we don't.

[funprogrammer]

Cool, got it, thanks @cire.