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| class WordFilter {
private static class Trie {
private final Trie[] children;
private final List<Integer> prefixIndexList;
private final List<Integer> suffixIndexList;
public Trie() {
this.children = new Trie[26];
this.prefixIndexList = new ArrayList<>();
this.suffixIndexList = new ArrayList<>();
}
public void insert(String word, int wordIndex) {
Trie node = this;
for (int i = 0; i < word.length(); i++) {
int index = word.charAt(i) - 'a';
if (node.children[index] == null) {
node.children[index] = new Trie();
}
node = node.children[index];
node.prefixIndexList.add(wordIndex);
}
}
public void reverseInsert(String word, int wordIndex) {
Trie node = this;
for (int i = word.length() - 1; i >= 0; i--) {
int index = word.charAt(i) - 'a';
if (node.children[index] == null) {
node.children[index] = new Trie();
}
node = node.children[index];
node.suffixIndexList.add(wordIndex);
}
}
public int search(String pref, String suff) {
Trie node = this;
for (int i = 0; i < pref.length() && node != null; i++) {
int index = pref.charAt(i) - 'a';
node = node.children[index];
}
if (node == null || node.prefixIndexList.isEmpty()) {
return -1;
}
List<Integer> indexListA = node.prefixIndexList;
node = this;
for (int i = suff.length() - 1; i >= 0 && node != null; i--) {
int index = suff.charAt(i) - 'a';
node = node.children[index];
}
if (node == null || node.suffixIndexList.isEmpty()) {
return -1;
}
List<Integer> indexListB = node.suffixIndexList;
int i = indexListA.size() - 1, j = indexListB.size() - 1;
while (i >= 0 && j >= 0) {
int indexA = indexListA.get(i);
int indexB = indexListB.get(j);
if (indexA < indexB) {
j--;
} else if (indexA > indexB) {
i--;
} else {
return indexA;
}
}
return -1;
}
}
private final Trie trie;
public WordFilter(String[] words) {
this.trie = new Trie();
for (int i = 0; i < words.length; i++) {
trie.insert(words[i], i);
trie.reverseInsert(words[i], i);
}
}
public int f(String pref, String suff) {
return trie.search(pref, suff);
}
}
|
References
745. Prefix and Suffix Search