solution: design add and search words and data structure

Author: Jeongwon Na

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

@@ -0,0 +1,63 @@
+class WordDictionary {
+    private static class CharDictionary {
+        HashMap<Character, CharDictionary> charMap;
+        boolean isEnd;
+
+        private CharDictionary() {
+            this.charMap = new HashMap<>();
+            this.isEnd = false;
+        }
+    }
+
+    private CharDictionary rootNode;
+
+    public WordDictionary() {
+        this.rootNode = new CharDictionary();
+    }
+
+    public void addWord(String word) {
+        CharDictionary currentNode = this.rootNode;
+
+        for (char ch : word.toCharArray()) {
+            if (!currentNode.charMap.containsKey(ch)) {
+                currentNode.charMap.put(ch, new CharDictionary());
+            }
+            currentNode = currentNode.charMap.get(ch);
+        }
+        currentNode.isEnd = true;
+    }
+
+    public boolean search(String word) {
+        return searchRecursive(word, this.rootNode, 0);
+    }
+
+    private boolean searchRecursive(String word, CharDictionary node, int index) {
+        // Base case
+        if (index == word.length()) {
+            return node.isEnd;
+        }
+
+        char ch = word.charAt(index);
+
+        if (ch == '.') {
+            for (CharDictionary childNode : node.charMap.values()) {
+                if (searchRecursive(word, childNode, index + 1)) {
+                    return true;
+                }
+            }
+            return false;
+        } else {
+            if (!node.charMap.containsKey(ch)) {
+                return false;
+            }
+            return searchRecursive(word, node.charMap.get(ch), index + 1);
+        }
+    }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * WordDictionary obj = new WordDictionary();
+ * obj.addWord(word);
+ * boolean param_2 = obj.search(word);
+ */