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GeezerVison is showing github.com — programming/problems/string/Trie.java at master · rp-code9/programming

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/*
* Trie data structure for string symbol table
*/
import java.util.NoSuchElementException;
public class Trie<Value> {
private static final int R = 26; // Extended ASCII char set
private Node root; // root of trie
private int n; // number of keys in trie
// R-way Node object
private static class Node {
private Object value;
Node[] next;
public Node() {
next = new Node[R];
value = null;
}
}
public Trie() {
root = null;
n = 0;
}
public Value search(String key) {
if (key == null) {
throw new IllegalArgumentException();
}
if (root == null) {
throw new NoSuchElementException();
}
Node temp = root;
for (int i = 0; i < key.length(); ++i) {
int index = key.charAt(i) - 'a';
if (temp.next[index] == null) {
return null;
}
temp = temp.next[index];
}
return (Value)temp.value;
}
public boolean contains(String key) {
return search(key) != null;
}
public void insert(String key, Value value) {
if (key == null || value == null) {
throw new IllegalArgumentException();
}
if (root == null) {
root = new Node();
}
Node temp = root;
int length = key.length();
for (int i = 0; i < length; ++i) {
int index = key.charAt(i) - 'a';
if (temp.next[index] == null) {
temp.next[index] = new Node();
}
temp = temp.next[index];
}
temp.value = value;
n++;
}
private boolean empty(Node node) {
for (int i = 0; i < R; ++i) {
if (node.next[i] != null) {
return false;
}
}
return true;
}
private Node remove(Node node, String key, int depth) {
if (node == null) {
return null;
}
if (depth == key.length()) {
if (node.value != null) {
n--;
node.value = null;
}
} else {
int index = key.charAt(depth) - 'a';
node.next[index] = remove(node.next[index], key, depth + 1);
}
if (node.value != null || !empty(node)) {
return node;
}
return null;
}
public void remove(String key) {
if (key == null) {
throw new IllegalArgumentException();
}
if (root == null) {
throw new NoSuchElementException();
}
root = remove(root, key, 0);
}
public int size() {
return n;
}
public boolean isEmpty() {
return size() == 0;
}
public static void main(String[] args) {
String[] keys = {"the", "a", "there", "answer", "any",
"by", "bye", "their", "z"};
Trie<Integer> trie = new Trie<>();
for (int i = 0; i < keys.length; ++i) {
trie.insert(keys[i], i);
}
System.out.println("== Trie size : " + trie.size());
for (int i = 0; i < keys.length; ++i) {
if (trie.contains(keys[i])) {
System.out.println(keys[i] + ": " + trie.search(keys[i]));
} else {
System.out.println(keys[i] + ": " + null);
}
}
String[] remove = {"z", "the", "their"};
for (int i = 0; i < remove.length; ++i) {
System.out.println("Deleting " + remove[i]);
trie.remove(remove[i]);
}
System.out.println("== Trie size : " + trie.size());
for (int i = 0; i < keys.length; ++i) {
if (trie.contains(keys[i])) {
System.out.println(keys[i] + ": " + trie.search(keys[i]));
} else {
System.out.println(keys[i] + ": " + null);
}
}
}
}
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