feat: add swift implementation to lcci problem: No.03.04 (doocs#2642)

Author: klever34

lcci/03.04.Implement Queue using Stacks/README.md

@@ -299,6 +299,52 @@ impl MyQueue {
  */
 ```
 
+```swift
+class MyQueue {
+    private var stk1: [Int] = []
+    private var stk2: [Int] = []
+
+    init() {}
+
+    func push(_ x: Int) {
+        stk1.append(x)
+    }
+
+    @discardableResult
+    func pop() -> Int {
+        move()
+        return stk2.removeLast()
+    }
+
+    func peek() -> Int {
+        move()
+        return stk2.last!
+    }
+
+    func empty() -> Bool {
+        return stk1.isEmpty && stk2.isEmpty
+    }
+
+    private func move() {
+        if stk2.isEmpty {
+            while !stk1.isEmpty {
+                stk2.append(stk1.removeLast())
+            }
+        }
+    }
+}
+
+/**
+ * Your MyQueue object will be instantiated and called as such:
+ * let obj = new MyQueue();
+ * obj.push(x);
+ * let param_2 = obj.pop();
+ * let param_3 = obj.peek();
+ * var myValue : Bool
+ * myValue = obj.empty();
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/03.04.Implement Queue using Stacks/README_EN.md

@@ -330,6 +330,52 @@ impl MyQueue {
  */
 ```
 
+```swift
+class MyQueue {
+    private var stk1: [Int] = []
+    private var stk2: [Int] = []
+
+    init() {}
+
+    func push(_ x: Int) {
+        stk1.append(x)
+    }
+
+    @discardableResult
+    func pop() -> Int {
+        move()
+        return stk2.removeLast()
+    }
+
+    func peek() -> Int {
+        move()
+        return stk2.last!
+    }
+
+    func empty() -> Bool {
+        return stk1.isEmpty && stk2.isEmpty
+    }
+
+    private func move() {
+        if stk2.isEmpty {
+            while !stk1.isEmpty {
+                stk2.append(stk1.removeLast())
+            }
+        }
+    }
+}
+
+/**
+ * Your MyQueue object will be instantiated and called as such:
+ * let obj = new MyQueue();
+ * obj.push(x);
+ * let param_2 = obj.pop();
+ * let param_3 = obj.peek();
+ * var myValue : Bool
+ * myValue = obj.empty();
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/03.04.Implement Queue using Stacks/Solution.swift

@@ -0,0 +1,43 @@
+class MyQueue {
+    private var stk1: [Int] = []
+    private var stk2: [Int] = []
+
+    init() {}
+
+    func push(_ x: Int) {
+        stk1.append(x)
+    }
+
+    @discardableResult
+    func pop() -> Int {
+        move()
+        return stk2.removeLast()
+    }
+
+    func peek() -> Int {
+        move()
+        return stk2.last!
+    }
+
+    func empty() -> Bool {
+        return stk1.isEmpty && stk2.isEmpty
+    }
+
+    private func move() {
+        if stk2.isEmpty {
+            while !stk1.isEmpty {
+                stk2.append(stk1.removeLast())
+            }
+        }
+    }
+}
+
+/**
+ * Your MyQueue object will be instantiated and called as such:
+ * let obj = new MyQueue();
+ * obj.push(x);
+ * let param_2 = obj.pop();
+ * let param_3 = obj.peek();
+ * var myValue : Bool 
+ * myValue = obj.empty();
+ */