link
Trie
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42class StreamChecker {
class TrieNode {
boolean isWord;
TrieNode[] next = new TrieNode[26];
}
TrieNode root = new TrieNode();
StringBuilder sb = new StringBuilder();
public StreamChecker(String[] words) {
createTrie(words);
}
public boolean query(char letter) {
sb.append(letter);
TrieNode node = root;
for (int i = sb.length() - 1; i >= 0 && node != null; i--) {
char c = sb.charAt(i);
node = node.next[c - 'a'];
if (node != null && node.isWord) {
return true;
}
}
return false;
}
private void createTrie(String[] words) {
for (String s : words) {
TrieNode node = root;
int len = s.length();
for (int i = len - 1; i >= 0; i--) {
char c = s.charAt(i);
if (node.next[c - 'a'] == null) {
node.next[c - 'a'] = new TrieNode();
}
node = node.next[c - 'a'];
}
node.isWord = true;
}
}
}