Add Solution.java to problems 0211

Author: huaxu1024

Diff for: solution/0211. Add and Search Word - Data structure design/Solution.java

@@ -0,0 +1,69 @@
+class WordDictionary {
+
+    class TrieNode {
+        private TrieNode[] links;
+        private boolean end;
+
+        public TrieNode() {
+            this.links = new TrieNode[26];
+        }
+
+        public boolean contains(char c) {
+            return links[c - 'a'] != null;
+        }
+
+        public void put(char c, TrieNode trieNode) {
+            links[c - 'a'] = trieNode;
+        }
+
+        public TrieNode get(char c) {
+            return links[c - 'a'];
+        }
+    }
+
+    private TrieNode root;
+
+    /** Initialize your data structure here. */
+    public WordDictionary() {
+        root = new TrieNode();
+    }
+
+    /** Adds a word into the data structure. */
+    public void addWord(String word) {
+        TrieNode node = root;
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+            if (!node.contains(c)) {
+                node.put(c, new TrieNode());
+            }
+            node = node.get(c);
+        }
+        node.end = true;
+    }
+
+    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
+    public boolean search(String word) {
+        return searchHelp(word, root);
+    }
+
+    private boolean searchHelp(String word, TrieNode root) {
+        TrieNode node = root;
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+
+            if ('.' == c) {
+                for (int j = 0; j < node.links.length; j++) {
+                    if (node.links[j] != null && searchHelp(word.substring(i + 1), node.links[j])) {
+                        return true;
+                    }
+                }
+                return false;
+            }
+            if (!node.contains(c)) {
+                return false;
+            }
+            node = node.get(c);
+        }
+        return node != null && node.end;
+    }
+}