Trie Data Structure implemented

Author: gkcs

src/main/java/main/java/videos/Tries.java

@@ -0,0 +1,80 @@
+package main.java.videos;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Tries {
+ public static void main(String[] args) {
+ final List<String> setOfStrings = new ArrayList<>();
+ setOfStrings.add("pqrs");
+ setOfStrings.add("pprt");
+ setOfStrings.add("psst");
+ setOfStrings.add("qqrs");
+ setOfStrings.add("pqrs");
+ final Trie trie = new Trie();
+ setOfStrings.forEach(trie::insert);
+ System.out.println(trie.query("psst"));
+ trie.update("qqrs", "psst");
+ System.out.println(trie.query("qqrs"));
+ System.out.println(trie.query("psst"));
+ }
+}
+
+class Trie {
+ final TrieNode root;
+
+ public Trie() {
+ this.root = new TrieNode();
+ }
+
+ public int query(final String s) {
+ TrieNode current = root;
+ for (int i = 0; i < s.length(); i++) {
+ if (current == null) {
+ return 0;
+ }
+ current = current.next(s.charAt(i));
+ }
+ return current.terminating;
+ }
+
+ public void insert(final String s) {
+ TrieNode current = root;
+ for (int i = 0; i < s.length(); i++) {
+ if (current.trieNodes[s.charAt(i) - 'a'] == null) {
+ current.trieNodes[s.charAt(i) - 'a'] = new TrieNode();
+ }
+ current = current.next(s.charAt(i));
+ }
+ current.terminating++;
+ }
+
+ public void delete(final String s) {
+ TrieNode current = root;
+ for (int i = 0; i < s.length(); i++) {
+ if (current == null) {
+ throw new RuntimeException();
+ }
+ current = current.next(s.charAt(i));
+ }
+ if (current.terminating != 0) {
+ current.terminating--;
+ } else {
+ throw new RuntimeException();
+ }
+ }
+
+ public void update(final String old, final String newString) {
+ delete(old);
+ insert(newString);
+ }
+}
+
+class TrieNode {
+ int terminating;
+ final TrieNode[] trieNodes = new TrieNode[26];
+
+ public TrieNode next(final char c) {
+ return trieNodes[c - 'a'];
+ }
+}