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Provides common utility functions
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/*
* Copyright (c) CQSE GmbH
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.conqat.lib.commons.tree;
import java.util.HashMap;
import java.util.Map;
import org.conqat.lib.commons.string.StringUtils;
/**
* Simple, efficient implementation of a trie that maps prefixes to objects of the generic type.
*/
public class Trie {
private class TrieNode {
private T value;
private Map next = new HashMap<>();
}
private TrieNode root = new TrieNode();
/**
* Map the prefix to the given value.
*/
public void put(String prefix, T value) {
TrieNode currentNode = root;
for (Character ch : StringUtils.splitChars(prefix)) {
TrieNode nextNode = currentNode.next.get(ch);
if (nextNode == null) {
nextNode = new TrieNode();
currentNode.next.put(ch, nextNode);
}
currentNode = nextNode;
}
currentNode.value = value;
}
/**
* Returns the value associated with the longest known prefix of this sequence, or null if no known
* prefix exists.
*/
public T getLongestPrefix(String sequence) {
T currentBestMatch = null;
TrieNode currentNode = root;
for (Character ch : StringUtils.splitChars(sequence)) {
currentNode = currentNode.next.get(ch);
if (currentNode == null) {
// Reached a leaf node in the Trie
return currentBestMatch;
} else if (currentNode.value != null) {
currentBestMatch = currentNode.value;
}
}
return currentBestMatch;
}
}