feat: add swift implementation to lcof2 problem: No.066 (doocs#3180)

Author: klever34

lcof2/剑指 Offer II 066. 单词之和/README.md

@@ -196,6 +196,34 @@ func (this *MapSum) Sum(prefix string) int {
  */
 ```
 
+#### Swift
+
+```swift
+class MapSum {
+    private var data: [String: Int]
+    private var t: [String: Int]
+
+    init() {
+        data = [String: Int]()
+        t = [String: Int]()
+    }
+
+    func insert(_ key: String, _ val: Int) {
+        let old = t[key] ?? 0
+        t[key] = val
+        for i in 1...key.count {
+            let endIndex = key.index(key.startIndex, offsetBy: i)
+            let k = String(key[key.startIndex..<endIndex])
+            data[k, default: 0] += (val - old)
+        }
+    }
+
+    func sum(_ prefix: String) -> Int {
+        return data[prefix] ?? 0
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 066. 单词之和/Solution.swift

@@ -0,0 +1,23 @@
+class MapSum {
+    private var data: [String: Int]
+    private var t: [String: Int]
+
+    init() {
+        data = [String: Int]()
+        t = [String: Int]()
+    }
+
+    func insert(_ key: String, _ val: Int) {
+        let old = t[key] ?? 0
+        t[key] = val
+        for i in 1...key.count {
+            let endIndex = key.index(key.startIndex, offsetBy: i)
+            let k = String(key[key.startIndex..<endIndex])
+            data[k, default: 0] += (val - old)
+        }
+    }
+
+    func sum(_ prefix: String) -> Int {
+        return data[prefix] ?? 0
+    }
+}