From 6b5049883b99aeed7179146d732c3863c5e70283 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9E=81=E5=AE=A2=E5=AD=A6=E4=BC=9F?= <qxuewei@yeah.net>
Date: Tue, 7 Dec 2021 14:47:48 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20239.=20=E6=BB=91=E5=8A=A8?=
 =?UTF-8?q?=E7=AA=97=E5=8F=A3=E6=9C=80=E5=A4=A7=E5=80=BC=20Swift=E7=89=88?=
 =?UTF-8?q?=E6=9C=AC?=
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---
 problems/0239.滑动窗口最大值.md | 106 +++++++++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/problems/0239.滑动窗口最大值.md b/problems/0239.滑动窗口最大值.md
index 8a8d3a52..1f245699 100644
--- a/problems/0239.滑动窗口最大值.md
+++ b/problems/0239.滑动窗口最大值.md
@@ -418,6 +418,112 @@ var maxSlidingWindow = function (nums, k) {
 };
 ```
 
+Swift:
+```Swift
+/// 双向链表
+class DoublyListNode {
+    var head: DoublyListNode?
+    var tail: DoublyListNode?
+    var next: DoublyListNode?
+    var pre: DoublyListNode?
+    var value: Int = 0
+    init(_ value: Int = 0) {
+        self.value = value
+    }
+    func isEmpty() -> Bool {
+        return self.head == nil
+    }
+    func first() -> Int? {
+        return self.head?.value
+    }
+    func last() -> Int? {
+        return self.tail?.value
+    }
+    func removeFirst() {
+        if isEmpty() {
+            return
+        }
+        let next = self.head!.next
+        self.head?.next = nil// 移除首节点
+        next?.pre = nil
+        self.head = next
+    }
+    func removeLast() {
+        if let tail = self.tail {
+            if let pre = tail.pre {
+                self.tail?.pre = nil
+                pre.next = nil
+                self.tail = pre
+            } else {
+                self.head = nil
+                self.tail = nil
+            }
+        }
+    }
+    func append(_ value: Int) {
+        let node = DoublyListNode(value)
+        if self.head != nil {
+            node.pre = self.tail
+            self.tail?.next = node
+            self.tail = node
+        } else {
+            self.head = node
+            self.tail = node
+            self.pre = nil
+            self.next = nil
+        }
+    }
+}
+// 单调队列, 从大到小
+class MyQueue {
+//    var queue: [Int]!// 用数组会超时
+    var queue: DoublyListNode!
+    init() {
+//        queue = [Int]()
+        queue = DoublyListNode()
+    }
+    // 滑动窗口时弹出第一个元素, 如果相等再弹出
+    func pop(x: Int) {
+        if !queue.isEmpty() && front() == x {
+            queue.removeFirst()
+        }
+    }
+    // 滑动窗口时添加下一个元素, 移除队尾比 x 小的元素 始终保证队头 > 队尾
+    func push(x: Int) {
+        while !queue.isEmpty() && queue.last()! < x {
+            queue.removeLast()
+        }
+        queue.append(x)
+    }
+    // 此时队头就是滑动窗口最大值
+    func front() -> Int {
+        return queue.first() ?? -1
+    }
+}
+
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        // 存放结果
+        var res = [Int]()
+        let queue = MyQueue()
+        // 先将前K个元素放入队列
+        for i in 0 ..< k {
+            queue.push(x: nums[i])
+        }
+        // 添加当前队列最大值到结果数组
+        res.append(queue.front())
+        for i in k ..< nums.count {
+            // 滑动窗口移除最前面元素
+            queue.pop(x: nums[i - k])
+            // 滑动窗口添加下一个元素
+            queue.push(x: nums[i])
+            // 保存当前队列最大值
+            res.append(queue.front())
+        }
+        return res
+    }
+}
+```
 
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