Improved trie code + leetcode longest word done

Author: rampatra

src/main/java/com/leetcode/trie/LongestWord.java

@@ -0,0 +1,77 @@
+package com.leetcode.trie;
+
+import java.util.HashMap;
+import java.util.Stack;
+
+/**
+ * Leetcode Problem: https://leetcode.com/problems/longest-word-in-dictionary/
+ *
+ * @author rampatra
+ * @since 2019-04-10
+ */
+public class LongestWord {
+
+    private class TrieNode {
+        char ch;
+        HashMap<Character, TrieNode> children = new HashMap<>();
+        String completeWord; // to mark a complete word in the tri data structure
+
+        TrieNode(char ch) {
+            this.ch = ch;
+        }
+    }
+
+    private TrieNode root = new TrieNode('0');
+
+    /**
+     * Inserts {@code data} in trie.
+     *
+     * @param str
+     */
+    public void insert(String str) {
+        char c;
+        TrieNode curr = root;
+
+        for (int i = 0; i < str.length(); i++) {
+            c = str.charAt(i);
+            curr.children.putIfAbsent(c, new TrieNode(c));
+            curr = curr.children.get(c);
+        }
+
+        curr.completeWord = str;
+    }
+
+    public String longestWord(String[] words) {
+        for (int i = 0; i < words.length; i++) {
+            insert(words[i]);
+        }
+
+        return longestWord();
+    }
+
+    private String longestWord() {
+        String longestWord = "";
+        TrieNode curr;
+        Stack<TrieNode> stack = new Stack<>();
+        stack.addAll(root.children.values());
+
+        while (!stack.empty()) {
+            curr = stack.pop();
+            if (curr.completeWord != null) {
+                if (curr.completeWord.length() > longestWord.length() ||
+                        (curr.completeWord.length() == longestWord.length() &&
+                                curr.completeWord.compareTo(longestWord) < 0)) {
+                    longestWord = curr.completeWord;
+                }
+                stack.addAll(curr.children.values());
+            }
+        }
+        return longestWord;
+    }
+
+    public static void main(String[] args) {
+        LongestWord longestWord = new LongestWord();
+        System.out.println(longestWord.longestWord(new String[]{"w", "wo", "wor", "worl", "world"}));
+        System.out.println(longestWord.longestWord(new String[]{"a", "banana", "app", "appl", "ap", "apply", "apple"}));
+    }
+}

src/main/java/com/rampatra/base/Trie.java

@@ -19,47 +19,37 @@
  * @author rampatra
  * @since 9/22/15
  */
-public class Trie<E> {
+public class Trie {
 
     private class TrieNode<T> {
-        HashMap<T, TrieNode<T>> children;
+        char ch;
+        HashMap<T, TrieNode<T>> children = new HashMap<>();
         boolean isCompleteWord; // to mark a complete word in the tri data structure
 
-        TrieNode(HashMap<T, TrieNode<T>> children) {
-            this.children = children;
+        TrieNode(char ch) {
+            this.ch = ch;
         }
     }
 
     private TrieNode<Character> root;
 
     Trie() {
-        root = new TrieNode<>(new HashMap<>());
+        root = new TrieNode<>('0');
     }
 
     /**
      * Inserts {@code data} in trie.
      *
-     * @param data
+     * @param str
      */
-    public void insert(E data) {
-
-        int i = 0;
-        String str = data.toString();
+    public void insert(String str) {
+        char c;
         TrieNode<Character> curr = root;
 
-        while (i < str.length()) {
-            if (curr.children.get(str.charAt(i)) != null) {
-                curr = curr.children.get(str.charAt(i));
-                i++;
-            } else {
-                break;
-            }
-        }
-
-        while (i < str.length()) {
-            curr.children.put(str.charAt(i), new TrieNode<>(new HashMap<>()));
-            curr = curr.children.get(str.charAt(i));
-            i++;
+        for (int i = 0; i < str.length(); i++) {
+            c = str.charAt(i);
+            curr.children.putIfAbsent(c, new TrieNode<>(c));
+            curr = curr.children.get(c);
         }
 
         curr.isCompleteWord = true;
@@ -68,12 +58,11 @@ public void insert(E data) {
     /**
      * Searches {@code data} in trie.
      *
-     * @param data the value to search.
-     * @return {@code true} if {@code data} is present, {@code false} otherwise.
+     * @param str the value to search.
+     * @return {@code true} if {@code str} is present, {@code false} otherwise.
      */
-    public boolean search(E data) {
+    public boolean search(String str) {
 
-        String str = data.toString();
         TrieNode<Character> curr = root;
 
         for (int i = 0; i < str.length(); i++) {
@@ -88,7 +77,7 @@ public boolean search(E data) {
 
     // unit testing
     public static void main(String[] args) {
-        Trie<String> trie = new Trie<>();
+        Trie trie = new Trie();
         trie.insert("ram");
         trie.insert("r");
         trie.insert("rama");