Merge pull request #1338 from wzqwtt/patch13

添加（0232.用栈实现队列、0225.用队列实现栈）Scala版本

problems/0225.用队列实现栈.md

@@ -815,6 +815,89 @@ class MyStack {
     }
 }
 ```
+Scala:
 
+使用两个队列模拟栈:
+```scala
+import scala.collection.mutable
+
+class MyStack() {
+
+  val queue1 = new mutable.Queue[Int]()
+  val queue2 = new mutable.Queue[Int]()
+
+  def push(x: Int) {
+    queue1.enqueue(x)
+  }
+
+  def pop(): Int = {
+    var size = queue1.size
+    // 将queue1中的每个元素都移动到queue2
+    for (i <- 0 until size - 1) {
+      queue2.enqueue(queue1.dequeue())
+    }
+    var res = queue1.dequeue()
+    // 再将queue2中的每个元素都移动到queue1
+    while (!queue2.isEmpty) {
+      queue1.enqueue(queue2.dequeue())
+    }
+    res
+  }
+
+  def top(): Int = {
+    var size = queue1.size
+    for (i <- 0 until size - 1) {
+      queue2.enqueue(queue1.dequeue())
+    }
+    var res = queue1.dequeue()
+    while (!queue2.isEmpty) {
+      queue1.enqueue(queue2.dequeue())
+    }
+    // 最终还需要把res送进queue1
+    queue1.enqueue(res)
+    res
+  }
+
+  def empty(): Boolean = {
+    queue1.isEmpty
+  }
+}
+```
+使用一个队列模拟:
+```scala
+import scala.collection.mutable
+
+class MyStack() {
+
+  val queue = new mutable.Queue[Int]()
+
+  def push(x: Int) {
+    queue.enqueue(x)
+  }
+
+  def pop(): Int = {
+    var size = queue.size
+    for (i <- 0 until size - 1) {
+      queue.enqueue(queue.head) // 把头添到队列最后
+      queue.dequeue() // 再出队
+    }
+    queue.dequeue()
+  }
+
+  def top(): Int = {
+    var size = queue.size
+    var res = 0
+    for (i <- 0 until size) {
+      queue.enqueue(queue.head) // 把头添到队列最后
+      res = queue.dequeue() // 再出队
+    }
+    res
+  }
+
+  def empty(): Boolean = {
+    queue.isEmpty
+  }
+}
+```
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0232.用栈实现队列.md

@@ -495,6 +495,45 @@ void myQueueFree(MyQueue* obj) {
     obj->stackOutTop = 0;
 }
 ```
+Scala:
+```scala
+class MyQueue() {
+  import scala.collection.mutable
+  val stackIn = mutable.Stack[Int]() // 负责出栈
+  val stackOut = mutable.Stack[Int]() // 负责入栈
 
+  // 添加元素
+  def push(x: Int) {
+    stackIn.push(x)
+  }
+
+  // 复用代码，如果stackOut为空就把stackIn的所有元素都压入StackOut
+  def dumpStackIn(): Unit = {
+    if (!stackOut.isEmpty) return
+    while (!stackIn.isEmpty) {
+      stackOut.push(stackIn.pop())
+    }
+  }
+
+  // 弹出元素
+  def pop(): Int = {
+    dumpStackIn()
+    stackOut.pop()
+  }
+
+  // 获取队头
+  def peek(): Int = {
+    dumpStackIn()
+    val res: Int = stackOut.pop()
+    stackOut.push(res)
+    res
+  }
+
+  // 判断是否为空
+  def empty(): Boolean = {
+    stackIn.isEmpty && stackOut.isEmpty
+  }
+}
+```
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>