design-add-and-search-words-data-structure

Author: taekwon-dev

design-add-and-search-words-data-structure/taekwon-dev.java

@@ -0,0 +1,58 @@
+class WordDictionary {
+
+    private class TrieNode {
+        Map<Character, TrieNode> children = new HashMap<>();
+        boolean isEndOfWord = false;
+    }
+
+    private TrieNode root;
+
+    public WordDictionary() {
+        root = new TrieNode();
+    }
+
+    /**
+     *  시간 복잡도: O(n), n = 단어의 길이
+     *  공간 복잡도: O(n)
+     */
+    public void addWord(String word) {
+        TrieNode node = root;
+
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+            node.children.putIfAbsent(c, new TrieNode());
+            node = node.children.get(c);
+        }
+        node.isEndOfWord = true;
+    }
+
+    /**
+     *  시간 복잡도: O(26^n), n = 단어의 길이
+     *  공간 복잡도: O(n)
+     */
+    public boolean search(String word) {
+        return searchInNode(word, 0, root);
+    }
+
+    private boolean searchInNode(String word, int index, TrieNode node) {
+        if (index == word.length()) {
+            return node.isEndOfWord;
+        }
+
+        char c = word.charAt(index);
+        if (c != '.') {
+            if (node.children.containsKey(c)) {
+                return searchInNode(word, index + 1, node.children.get(c));
+            } else {
+                return false;
+            }
+        } else {
+            for (TrieNode childNode : node.children.values()) {
+                if (searchInNode(word, index + 1, childNode)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+    }
+}