feat: add swift implementation to lcof problem: No.30 (doocs#2897)

Author: klever34

lcof/面试题30. 包含min函数的栈/README.md

@@ -399,6 +399,47 @@ public class MinStack {
  */
 ```
 
+#### Swift
+
+```swift
+class MinStack {
+    private var stack: [Int]
+    private var minStack: [Int]
+
+    init() {
+        stack = []
+        minStack = [Int.max]
+    }
+
+    func push(_ x: Int) {
+        stack.append(x)
+        minStack.append(min(x, minStack.last!))
+    }
+
+    func pop() {
+        stack.removeLast()
+        minStack.removeLast()
+    }
+
+    func top() -> Int {
+        return stack.last!
+    }
+
+    func getMin() -> Int {
+        return minStack.last!
+    }
+}
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * let obj = MinStack();
+ * obj.push(x);
+ * obj.pop();
+ * let param_3 = obj.top();
+ * let param_4 = obj.getMin();
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题30. 包含min函数的栈/Solution.swift

@@ -0,0 +1,36 @@
+class MinStack {
+    private var stack: [Int]
+    private var minStack: [Int]
+
+    init() {
+        stack = []
+        minStack = [Int.max]
+    }
+
+    func push(_ x: Int) {
+        stack.append(x)
+        minStack.append(min(x, minStack.last!))
+    }
+
+    func pop() {
+        stack.removeLast()
+        minStack.removeLast()
+    }
+
+    func top() -> Int {
+        return stack.last!
+    }
+
+    func getMin() -> Int {
+        return minStack.last!
+    }
+}
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * let obj = MinStack();
+ * obj.push(x);
+ * obj.pop();
+ * let param_3 = obj.top();
+ * let param_4 = obj.getMin();
+ */