Design add and search words structure

Author: TonyKim9401

design-add-and-search-words-data-structure/TonyKim9401.java

@@ -0,0 +1,56 @@
+// SC: O(n)
+// -> n is the length of the given String
+// TC: O(n * 26)
+// -> n is the length of the given String * the number of alphabets
+class TrieNode {
+    TrieNode[] childNode;
+    boolean isEndOfWord;
+
+    public TrieNode() {
+        childNode = new TrieNode[26];
+        isEndOfWord = false;
+    }
+}
+
+class WordDictionary {
+
+    private TrieNode root;
+
+    public WordDictionary() {
+        root = new TrieNode();
+    }
+
+    public void addWord(String word) {
+        TrieNode node = root;
+
+        for (char c : word.toCharArray()) {
+            int idx = c - 'a';
+            if (node.childNode[idx] == null) {
+                node.childNode[idx] = new TrieNode();
+            }
+            node = node.childNode[idx];
+        }
+        node.isEndOfWord = true;
+    }
+
+    public boolean search(String word) {
+        return searchInNode(word.toCharArray(), 0, root);
+    }
+
+    private boolean searchInNode(char[] word, int idx, TrieNode node) {
+        if (idx == word.length) return node.isEndOfWord;
+
+        char c = word[idx];
+
+        if (c == '.') {
+            for (TrieNode child : node.childNode) {
+                if (child != null && searchInNode(word, idx+1, child)) return true;
+            }
+            return false;
+        } else {
+            int childIdx = c - 'a';
+            if (node.childNode[childIdx] == null) return false;
+            return searchInNode(word, idx+1, node.childNode[childIdx]);
+        }
+    }
+}