public boolean isWord(String prefix) {
return myPrefixTrie.isWord(prefix);
}
private boolean add(String s, int index) {
if (index == s.length()) {
if (isWord) {
return false;
}
isWord = true;
return true;
}
char c = s.charAt(index);
for (int i = 0; i < numChildren; i++) {
if (child[i].ch == c) {
return child[i].add(s, index + 1);
}
}
// this code adds from the bottom to the top because the addChild method
// checks for cyclic references. This prevents quadratic runtime.
int i = s.length() - 1;
Trie t = createNode(s.charAt(i--));
t.isWord = true;
while (i >= index) {
Trie n = createNode(s.charAt(i--));
n.addChild(t);
t = n;
}
addChild(t);
return true;
}
/**
* Removes the specified string from the trie. Returns true if the string was removed or false if
* the string was not a word in the trie.
*
* @param s String.
* @return true or false.
*/
public boolean remove(String s) {
Trie t = getNode(s);
if ((t == null) || !t.isWord) {
return false;
}
t.isWord = false;
while ((t != null) && (t.numChildren == 0) && !t.isWord) {
Trie p = t.parent;
if (p != null) {
p.removeChild(t);
}
t = p;
}
return true;
}
/**
* Removes all words from the trie that begin with the specified prefix. Returns true if the trie
* contained the prefix, false otherwise.
*
* @param prefix String.
* @return true or false.
*/
public boolean removeAll(String prefix) {
Trie t = getNode(prefix);
if (t == null) {
return false;
}
if (t.parent == null) {
if ((t.numChildren == 0) && !t.isWord) {
return false;
}
for (int i = 0; i < t.numChildren; i++) {
t.child[i].parent = null;
t.child[i] = null;
}
t.numChildren = 0;
t.isWord = false;
return true;
}
Trie p = t.parent;
p.removeChild(t);
t = p;
while ((t != null) && (t.numChildren == 0) && !t.isWord) {
p = t.parent;
if (p != null) {
p.removeChild(t);
}
t = p;
}
return true;
}
