design add and search words data structure solution

Author: radiantchoi

design-add-and-search-words-data-structure/radiantchoi.swift

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+class WordDictionary {
+    let root: TrieNode
+
+    init() {
+        root = TrieNode()
+    }
+    
+    func addWord(_ word: String) {
+        let spread = Array(word)
+        var node = root
+
+        for letter in spread {
+            if let child = node.children[letter] {
+                node = child
+            } else {
+                let newNode = TrieNode()
+                node.children[letter] = newNode
+                node = newNode
+            }
+        }
+
+        node.isTerminating = true
+    }
+    
+    func search(_ word: String) -> Bool {
+        return traverse(root, Array(word), 0)
+    }
+
+    private func traverse(_ node: TrieNode, _ quote: [Character], _ starting: Int) -> Bool {
+        if starting == quote.count {
+            return node.isTerminating
+        }
+
+        let letter = quote[starting]
+
+        if letter == "." {
+            var result = false
+
+            for key in node.children.keys {
+                if let child = node.children[key] {
+                    result = result || traverse(child, quote, starting + 1)
+                }
+            }
+
+            return result
+        } else {
+            guard let child = node.children[letter] else {
+                return false
+            }
+
+            return traverse(child, quote, starting + 1)
+        }
+    }
+}
+
+class TrieNode {
+    var isTerminating: Bool
+    var children: [Character: TrieNode]
+
+    init(isTerminating: Bool = false, children: [Character: TrieNode] = [:]) {
+        self.isTerminating = isTerminating
+        self.children = children
+    }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * let obj = WordDictionary()
+ * obj.addWord(word)
+ * let ret_2: Bool = obj.search(word)
+ */