Design Add and Search Words Data Structure

Author: forest000014

design-add-and-search-words-data-structure/forest000014.java

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+/*
+Time Complexity:
+- add: O(w)
+- search: O(26^2 * w) = O(w)
+Space Complexity: O(w)
+
+Trie를 활용하되, '.'의 탐색이 필요한 경우에는 for문을 사용한다.
+
+*/
+class WordDictionary {
+    class Node {
+        public char ch;
+        public boolean ends;
+        public Map<Character, Node> children;
+
+        Node() {
+            this.children = new HashMap<>();
+        }
+
+        Node(char ch) {
+            this.ch = ch;
+            this.children = new HashMap<>();
+        }
+    }
+
+    Node root;
+
+    public WordDictionary() {
+        this.root = new Node();
+    }
+
+    public void addWord(String word) {
+        Node curr = this.root;
+
+        for (int i = 0; i < word.length(); i++) {
+            char ch = word.charAt(i);
+            if (!curr.children.containsKey(ch)) {
+                curr.children.put(ch, new Node(ch));
+            }
+
+            if (i == word.length() - 1) {
+                curr.children.get(ch).ends = true;
+            } else {
+                curr = curr.children.get(ch);
+            }
+        }
+    }
+
+    public boolean search(String word) {
+        return searchChar(word, 0, this.root);
+    }
+
+    private boolean searchChar(String word, int idx, Node curr) {
+        if (curr == null) {
+            return false;
+        } else if (idx == word.length()) {
+            return curr.ends;
+        }
+
+        char ch = word.charAt(idx);
+
+        if (ch == '.') {
+            for (Character key : curr.children.keySet()) {
+                if (searchChar(word, idx + 1, curr.children.get(key))) {
+                    return true;
+                }
+            }
+            return false;
+        } else {
+            return searchChar(word, idx + 1, curr.children.get(ch));
+        }
+    }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * WordDictionary obj = new WordDictionary();
+ * obj.addWord(word);
+ * boolean param_2 = obj.search(word);
+ */