[Design] Add a solution to Add and Search Word - Data structure design

Design/AddSearchWord.swift

@@ -0,0 +1,83 @@
+/**
+ * Question Link: https://leetcode.com/problems/add-and-search-word-data-structure-design/
+ * Primary idea: Use trie to add and search word. For '.' case we iterate through all sub nodes.
+ *
+ * Time Complexity: addWord - O(n), n stands for the length of the word; search - O(24^n)
+ * Space Complexity: addWord - O(n), search - O(1)
+ *
+ */
+
+
+class WordDictionary {
+
+    var head: TrieNode
+
+    /** Initialize your data structure here. */
+    init() {
+        head = TrieNode()
+    }
+
+    /** Adds a word into the data structure. */
+    func addWord(_ word: String) {
+        var node = head
+
+        for char in word {
+            if node.children[char] == nil {
+                node.children[char] = TrieNode()
+            }
+
+            node = node.children[char]!
+        }
+
+        node.isEnd = true
+    }
+
+    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
+    func search(_ word: String) -> Bool {
+        return search(word, head)
+    }
+
+    private func search(_ word: String, _ startNode: TrieNode) -> Bool {
+        var node = startNode
+
+        guard let char = word.first else {
+            return node.isEnd
+        }
+
+        if char != "." {
+            if node.children[char] == nil {
+                return false
+            } else {
+                return search(String(word.dropFirst()), node.children[char]!)
+            }
+        } else {
+            if node.children.isEmpty {
+                return false
+            } else {
+                for childNode in node.children.values {
+                    if search(String(word.dropFirst()), childNode) {
+                        return true
+                    }
+                }
+                return false
+            }
+        }
+    }
+}
+
+class TrieNode {
+    var isEnd: Bool
+    var children: [Character: TrieNode]
+
+    init() {
+        isEnd = false
+        children = [Character: TrieNode]()
+    }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * let obj = WordDictionary()
+ * obj.addWord(word)
+ * let ret_2: Bool = obj.search(word)
+ */

README.md

@@ -4,7 +4,7 @@
 ![Leetcode](./logo.png?style=centerme)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 298 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
+[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 299 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
 
 ## Contributors
 
@@ -382,6 +382,7 @@
 [Design Tic-Tac-Toe](https://leetcode.com/problems/design-tic-tac-toe/| [Swift](./Design/DesignTicTacToe.swift)| Medium| O(1)| O(n)|
 [Flatten 2D Vector](https://leetcode.com/problems/flatten-2d-vector/)| [Swift](./Design/Vector2D.swift)| Medium | O(n)| O(n)|
 [Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/)| [Swift](./Design/ImplementTrie.swift)| Medium | O(n)| O(n)|
+[Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/)| [Swift](./Design/AddSearchWord.swift)| Medium | O(24^n)| O(n)|
 [Insert Delete GetRandom O(1)](https://leetcode.com/problems/insert-delete-getrandom-o1/)| [Swift](./Design/InsertDeleteGetRandom.swift)| Medium| O(1)| O(n)|
 [LRU Cache](https://leetcode.com/problems/lru-cache/)| [Swift](./Design/LRUCache.swift)| Hard| O(1)| O(n)|