From ea77b6b865471f9dce346da9e994421ebc81c6dc Mon Sep 17 00:00:00 2001
From: Yi Gu <rio.deliberate@gmail.com>
Date: Sun, 8 Apr 2018 15:34:59 +0800
Subject: [PATCH] [DFS] Add a solution to Add and Search Word - Data structure
 design

---
 DFS/WordDictionary.swift | 79 ++++++++++++++++++++++++++++++++++++++++
 README.md                |  5 ++-
 2 files changed, 82 insertions(+), 2 deletions(-)
 create mode 100644 DFS/WordDictionary.swift

diff --git a/DFS/WordDictionary.swift b/DFS/WordDictionary.swift
new file mode 100644
index 00000000..cc1506d7
--- /dev/null
+++ b/DFS/WordDictionary.swift
@@ -0,0 +1,79 @@
+/**
+ * Question Link: https://leetcode.com/problems/add-and-search-word-data-structure-design/
+ * Primary idea: Trie with DFS to resolve search problem
+ * 
+ * Time Complexity: O(n), Space Complexity: O(n)
+ *
+ */
+
+class WordDictionary {
+  var trie = Trie()
+
+  func add(word: String) {
+    trie.add(word: word)
+  }
+
+  func search(word: String) -> Bool {
+    return trie.search(word:word)
+  }
+}
+
+class TrieNode {
+  var children: [Character: TrieNode]
+  var isEnd: Bool
+
+  init() {
+    self.children = [Character: TrieNode]()
+    self.isEnd = false
+  }
+}
+
+class Trie {
+  var root: TrieNode
+
+  init() {
+    root = TrieNode()
+  }
+
+  func add(word: String) {
+    var node = root
+
+    for char in word {
+      if node.children[char] == nil {
+        node.children[char] = TrieNode()
+      }
+
+      node = node.children[char]!
+    }
+
+    node.isEnd = true
+  }
+  
+  func search(word:String) -> Bool {
+    return dfsSearch(word: word, index: 0, node: root)
+  }
+  
+  fileprivate func dfsSearch(word: String, index: Int, node: TrieNode) -> Bool {
+    if index == word.count {
+      return node.isEnd
+    }
+    
+    let char = Array(word)[index]
+    
+    if char != "." {
+      guard let nextNode = node.children[char] else {
+        return false
+      }
+      
+      return dfsSearch(word: word, index: index + 1, node: nextNode)
+    } else{
+      for key in node.children.keys {
+        if dfsSearch(word: word, index: index + 1, node: node.children[key]!) {
+          return true
+        }
+      }
+      
+      return false
+    }
+  }
+}
\ No newline at end of file
diff --git a/README.md b/README.md
index 16ed587e..14ccc8ee 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@
 * [Microsoft](#microsoft)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 230 completed solutions. Note: questions with &hearts; mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
+[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 231 completed solutions. Note: questions with &hearts; mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
 
 
 ## Array
@@ -215,6 +215,7 @@
 [Walls and Gates](https://leetcode.com/problems/walls-and-gates/)| [Swift](./DFS/WallsGates.swift)| Medium| O(n!)| O(2^n)|
 [Word Search](https://leetcode.com/problems/word-search/)| [Swift](./DFS/WordSearch.swift)| Medium| O((n^2)!)| O(n^2)|
 [Word Search II](https://leetcode.com/problems/word-search-ii/)| [Swift](./DFS/WordSearchII.swift)| Hard| O(((mn)^2))| O(n^2)|
+[Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/)| [Swift](./DFS/WordDictionary.swift)| Medium| O(n)| O(n)|
 [N-Queens](https://leetcode.com/problems/n-queens/)| [Swift](./DFS/NQueens.swift)| Hard| O((n^4))| O(n^2)|
 [N-Queens II](https://leetcode.com/problems/n-queens-ii/)| [Swift](./DFS/NQueensII.swift)| Hard| O((n^3))| O(n)|
 [Sudoku Solver](https://leetcode.com/problems/sudoku-solver/)| [Swift](./DFS/SudokuSolver.swift)| Hard| O(n^4)| O(1)|
@@ -587,7 +588,7 @@
 |		|	214	|	[Shortest Palindrome](https://leetcode.com/problems/shortest-palindrome/)	|	Hard	|
 |	[Swift](./DP/HouseRobberII.swift)	|	213	|	[House Robber II](https://leetcode.com/problems/house-robber-ii/)	|	Medium	|
 | [Swift](./DFS/WordSearchII.swift)	|	212	|	[Word Search II](https://leetcode.com/problems/word-search-ii/)	|	Hard	|
-|		|	211	|	[Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/)	|	Medium	|
+|	[Swift](./DFS/WordDictionary.swift)	|	211	|	[Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/)	|	Medium	|
 |		|	210	|	[Course Schedule II](https://leetcode.com/problems/course-schedule-ii/)	|	Medium	|
 |	[Swift](./Array/MinimumSizeSubarraySum.swift)	|	209	|	[Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/)	|	Medium	|
 |		|	208	|	[Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/)	|	Medium	|