feat: add swift implementation to lcof2 problem: No.062

Author: klever34

lcof2/剑指 Offer II 062. 实现前缀树/README.md

@@ -418,6 +418,62 @@ public class Trie {
  */
 ```
 
+#### Swift
+
+```swift
+class Trie {
+    private var children: [Trie?]
+    private var isEnd: Bool
+
+    init() {
+        self.children = Array(repeating: nil, count: 26)
+        self.isEnd = false
+    }
+
+    func insert(_ word: String) {
+        var node = self
+        for char in word {
+            let index = Int(char.asciiValue! - Character("a").asciiValue!)
+            if node.children[index] == nil {
+                node.children[index] = Trie()
+            }
+            node = node.children[index]!
+        }
+        node.isEnd = true
+    }
+
+    func search(_ word: String) -> Bool {
+        if let node = searchPrefix(word) {
+            return node.isEnd
+        }
+        return false
+    }
+
+    func startsWith(_ prefix: String) -> Bool {
+        return searchPrefix(prefix) != nil
+    }
+
+    private func searchPrefix(_ prefix: String) -> Trie? {
+        var node = self
+        for char in prefix {
+            let index = Int(char.asciiValue! - Character("a").asciiValue!)
+            if node.children[index] == nil {
+                return nil
+            }
+            node = node.children[index]!
+        }
+        return node
+    }
+}
+/**
+ * Your Trie object will be instantiated and called as such:
+ * let trie = Trie()
+ * trie.insert(word);
+ * trie.search(word);
+ * trie.startsWith(prefix);
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 062. 实现前缀树/Solution.swift

@@ -0,0 +1,51 @@
+class Trie {
+    private var children: [Trie?]
+    private var isEnd: Bool
+
+    init() {
+        self.children = Array(repeating: nil, count: 26)
+        self.isEnd = false
+    }
+
+    func insert(_ word: String) {
+        var node = self
+        for char in word {
+            let index = Int(char.asciiValue! - Character("a").asciiValue!)
+            if node.children[index] == nil {
+                node.children[index] = Trie()
+            }
+            node = node.children[index]!
+        }
+        node.isEnd = true
+    }
+
+    func search(_ word: String) -> Bool {
+        if let node = searchPrefix(word) {
+            return node.isEnd
+        }
+        return false
+    }
+
+    func startsWith(_ prefix: String) -> Bool {
+        return searchPrefix(prefix) != nil
+    }
+
+    private func searchPrefix(_ prefix: String) -> Trie? {
+        var node = self
+        for char in prefix {
+            let index = Int(char.asciiValue! - Character("a").asciiValue!)
+            if node.children[index] == nil {
+                return nil
+            }
+            node = node.children[index]!
+        }
+        return node
+    }
+}
+/**
+ * Your Trie object will be instantiated and called as such:
+ * let trie = Trie()
+ * trie.insert(word);
+ * trie.search(word);
+ * trie.startsWith(prefix);
+ */