Printing words from structure - c++

Question

For the following structure of a trie.
struct Trie {
bool eow; //when a Trie field isWord = true, hence there is a word
char letter;
Trie *letters[27];
};
I'm trying to create a function for an auto completion program, that basically prints out words in a trie given a specific string prefix
Here is what i have:
int wordcheck( TrieNode &node )
{
if (node.isWord == 1) // you have found your word, so return true
{
return 1;
}
for (int i = 0; i < 26; i++)
{
if (node.letters[i] != NULL && wordcheck(*(node.letters[i])))
{
return 1;
}
}
return 0;
}
string find (TrieNode &node, const string &word, string acc)
{
if (word.length() == 0)
{
string x = "";
if (node.isWord == 1){
x = " ";
int check = 1;
for(int i = 0; i < 26; i++)
{
if (node.letters[i] != NULL && wordcheck(*(node.letters[i])))
{
x = x + acc; check = 0; break;
}
}
if(check == 1)
{ return x; }
}
for (int i = 0; i < 26; i++){
if (node.letters[i] != NULL && wordcheck(*(node.letters[i])))
{
char let = (char)(i + (int)'a');
if (x[x.length() - 1 ] == ' ')
{
x = x + acc;
}
x = x + node.letters[i]->letter
+ find(*(node.letters[i]), word, acc + node.letters[i]->letter);
}
}
return x;
}
else if (node.letters[word[0] - 'a'] == NULL)
{ return ""; }
else {
return word[0] + find(*(node.letters[ word[0] - 'a']),
word.substr(1, word.length()-1),
acc + word[0]);
}
}
it seems to work other than the fact it if i give it a long prefix it will print words shorter than the prefix. I used accumulative recursion, and im sure there is a more efficient way of doing this. My question is if anyone could make it so that i return the right strings, or guide me through a easier algorithm if possible?

Answer 1

I'm trying to create a function for an auto completion program, that basically prints out words in a trie given a specific string prefix
I am not going to analyse your program - for me it is too complicated, e.g. I don't get any idea what wordcheck is supposed to do? Why is it not bool but int? Do you really need to check that your sub-trie has any word, do you really have non empty Trie without words in it?
For first - to print all words which begin with the given prefix - you need to go to the node where all these words begin:
TrieNode* TreeNode::get(std::string word)
{
TreeNode* retVal = this;
for (size_t i = 0; i < word.length(); ++i) {
if (Words[i] < 'a' || words[i] > 'z')
throw std::runtime_error("Wrong word");
if (retVal->letters[word[i] - 'a'] != NULL)
retVal = retVal->letters[word[i] - 'a'];
else
return nullptr;
}
return retVal;
}
You need the function which prints all the words from the given node:
void TreeNode::printAll(std::ostream& os, std::string prefix)
{
if (isWord)
os << prefix << "\n";
for (size_t i = 0; i < 26; ++i) {
if (retVal->letters[i] != NULL)
// this recursive call can be replaced with iterative solution with stack
letters[i]->print(os, prefix + char('a' + i));
}
}
And combining these functions - gives you what you want:
void TreeNode::printBeginWith(std::ostream& os, std::string prefix)
{
TreeNode* node = get(prefix);
if (node)
node->printAll(os, prefix);
}