From 8c394c9f8588a1e94250dc93bede24b7380996f8 Mon Sep 17 00:00:00 2001
From: ZongqinWang <1722249371@qq.com>
Date: Tue, 17 May 2022 17:08:11 +0800
Subject: [PATCH 1/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200150.=E9=80=86?=
=?UTF-8?q?=E6=B3=A2=E5=85=B0=E8=A1=A8=E8=BE=BE=E5=BC=8F=E6=B1=82=E5=80=BC?=
=?UTF-8?q?.md=20Scala=E7=89=88=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
---
problems/0150.逆波兰表达式求值.md | 29 ++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/problems/0150.逆波兰表达式求值.md b/problems/0150.逆波兰表达式求值.md
index fd3d69aa..47da06f6 100644
--- a/problems/0150.逆波兰表达式求值.md
+++ b/problems/0150.逆波兰表达式求值.md
@@ -325,6 +325,33 @@ func evalRPN(_ tokens: [String]) -> Int {
return stack.last!
}
```
-
+Scala:
+```scala
+object Solution {
+ import scala.collection.mutable
+ def evalRPN(tokens: Array[String]): Int = {
+ val stack = mutable.Stack[Int]() // 定义栈
+ // 抽取运算操作，需要传递x,y，和一个函数
+ def operator(x: Int, y: Int, f: (Int, Int) => Int): Int = f(x, y)
+ for (token <- tokens) {
+ // 模式匹配，匹配不同的操作符做什么样的运算
+ token match {
+ // 最后一个参数 _+_，代表x+y，遵循Scala的函数至简原则，以下运算同理
+ case "+" => stack.push(operator(stack.pop(), stack.pop(), _ + _))
+ case "-" => stack.push(operator(stack.pop(), stack.pop(), -_ + _))
+ case "*" => stack.push(operator(stack.pop(), stack.pop(), _ * _))
+ case "/" => {
+ var pop1 = stack.pop()
+ var pop2 = stack.pop()
+ stack.push(operator(pop2, pop1, _ / _))
+ }
+ case _ => stack.push(token.toInt) // 不是运算符就入栈
+ }
+ }
+ // 最后返回栈顶，不需要加return关键字
+ stack.pop()
+ }
+}
+```
-----------------------
From 748a728420be62c835866e7027171462ef90f888 Mon Sep 17 00:00:00 2001
From: ZongqinWang <1722249371@qq.com>
Date: Tue, 17 May 2022 18:41:52 +0800
Subject: [PATCH 2/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200239.=E6=BB=91?=
=?UTF-8?q?=E5=8A=A8=E7=AA=97=E5=8F=A3=E6=9C=80=E5=A4=A7=E5=80=BC.md=20Sca?=
=?UTF-8?q?la=E7=89=88=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
---
problems/0239.滑动窗口最大值.md | 47 ++++++++++++++++++++++++++
1 file changed, 47 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 f269450f..eb32fdd2 100644
--- a/problems/0239.滑动窗口最大值.md
+++ b/problems/0239.滑动窗口最大值.md
@@ -630,6 +630,53 @@ func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
return result
}
```
+Scala:
+```scala
+import scala.collection.mutable.ArrayBuffer
+object Solution {
+ def maxSlidingWindow(nums: Array[Int], k: Int): Array[Int] = {
+ var len = nums.length - k + 1 // 滑动窗口长度
+ var res: Array[Int] = new Array[Int](len) // 声明存储结果的数组
+ var index = 0 // 结果数组指针
+ val queue: MyQueue = new MyQueue // 自定义队列
+ // 将前k个添加到queue
+ for (i <- 0 until k) {
+ queue.add(nums(i))
+ }
+ res(index) = queue.peek // 第一个滑动窗口的最大值
+ index += 1
+ for (i <- k until nums.length) {
+ queue.poll(nums(i - k)) // 首先移除第i-k个元素
+ queue.add(nums(i)) // 添加当前数字到队列
+ res(index) = queue.peek() // 赋值
+ index+=1
+ }
+ // 最终返回res，return关键字可以省略
+ res
+ }
+}
+
+class MyQueue {
+ var queue = ArrayBuffer[Int]()
+
+ // 移除元素，如果传递进来的跟队头相等，那么移除
+ def poll(value: Int): Unit = {
+ if (!queue.isEmpty && queue.head == value) {
+ queue.remove(0)
+ }
+ }
+
+ // 添加元素，当队尾大于当前元素就删除
+ def add(value: Int): Unit = {
+ while (!queue.isEmpty && value > queue.last) {
+ queue.remove(queue.length - 1)
+ }
+ queue.append(value)
+ }
+
+ def peek(): Int = queue.head
+}
+```
-----------------------
From 47c4cc102123b1b43f09b7b766fdd2f1e1b979a9 Mon Sep 17 00:00:00 2001
From: ZongqinWang <1722249371@qq.com>
Date: Tue, 17 May 2022 19:52:32 +0800
Subject: [PATCH 3/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200347.=E5=89=8DK?=
=?UTF-8?q?=E4=B8=AA=E9=AB=98=E9=A2=91=E5=85=83=E7=B4=A0.md=20Scala?=
=?UTF-8?q?=E7=89=88=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
---
problems/0347.前K个高频元素.md | 42 ++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/problems/0347.前K个高频元素.md b/problems/0347.前K个高频元素.md
index 1d6a358b..20932b28 100644
--- a/problems/0347.前K个高频元素.md
+++ b/problems/0347.前K个高频元素.md
@@ -374,7 +374,49 @@ function topKFrequent(nums: number[], k: number): number[] {
};
```
+Scala:
+解法一: 优先级队列
+```scala
+object Solution {
+ import scala.collection.mutable
+ def topKFrequent(nums: Array[Int], k: Int): Array[Int] = {
+ val map = mutable.HashMap[Int, Int]()
+ // 将所有元素都放入Map
+ for (num <- nums) {
+ map.put(num, map.getOrElse(num, 0) + 1)
+ }
+ // 声明一个优先级队列，在函数柯里化那块需要指明排序方式
+ var queue = mutable.PriorityQueue[(Int, Int)]()(Ordering.fromLessThan((x, y) => x._2 > y._2))
+ // 将map里面的元素送入优先级队列
+ for (elem <- map) {
+ queue.enqueue(elem)
+ if(queue.size > k){
+ queue.dequeue // 如果队列元素大于k个，出队
+ }
+ }
+ // 最终只需要key的Array形式就可以了，return关键字可以省略
+ queue.map(_._1).toArray
+ }
+}
+```
+解法二: 相当于一个wordCount程序
+```scala
+object Solution {
+ def topKFrequent(nums: Array[Int], k: Int): Array[Int] = {
+ // 首先将数据变为(x,1)，然后按照x分组，再使用map进行转换(x,sum)，变换为Array
+ // 再使用sort针对sum进行排序，最后take前k个，再把数据变为x,y,z这种格式
+ nums.map((_, 1)).groupBy(_._1)
+ .map {
+ case (x, arr) => (x, arr.map(_._2).sum)
+ }
+ .toArray
+ .sortWith(_._2 > _._2)
+ .take(k)
+ .map(_._1)
+ }
+}
+```
-----------------------
