feat: add swift implementation to lcof2 problem: No.042 (#3052)

Author: klever34

lcof2/剑指 Offer II 042. 最近请求次数/README.md

@@ -213,6 +213,32 @@ RecentCounter.prototype.ping = function (t) {
  */
 ```
 
+#### Swift
+
+```swift
+class RecentCounter {
+    private var q: [Int]
+    
+    init() {
+        q = []
+    }
+    
+    func ping(_ t: Int) -> Int {
+        q.append(t)
+        while q.first! < t - 3000 {
+            q.removeFirst()
+        }
+        return q.count
+    }
+}
+
+/**
+ * Your RecentCounter object will be instantiated and called as such:
+ * let obj = RecentCounter()
+ * let param_1 = obj.ping(t)
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 042. 最近请求次数/Solution.swift

@@ -0,0 +1,21 @@
+class RecentCounter {
+    private var q: [Int]
+    
+    init() {
+        q = []
+    }
+    
+    func ping(_ t: Int) -> Int {
+        q.append(t)
+        while q.first! < t - 3000 {
+            q.removeFirst()
+        }
+        return q.count
+    }
+}
+
+/**
+ * Your RecentCounter object will be instantiated and called as such:
+ * let obj = RecentCounter()
+ * let param_1 = obj.ping(t)
+ */