add scala #117*

scala-leetcode/README.md

@@ -63,6 +63,7 @@ Leetcode Scala 实现
 * [最大二叉树 II](./src/main/scala/io/github/dreamylost/Leetcode_998.scala)
 * [先序遍历构造二叉树](./src/main/scala/io/github/dreamylost/Leetcode_1008.scala)
 * [填充每个节点的下一个右侧节点指针](./src/main/scala/io/github/dreamylost/Leetcode_116.scala)
+* [填充每个节点的下一个右侧节点指针 II](./src/main/scala/io/github/dreamylost/Leetcode_117.scala)
 
 ## 链表
 

scala-leetcode/src/main/scala/io/github/dreamylost/Leetcode_117.scala

+/* Licensed under Apache-2.0 @梦境迷离 */
+package io.github.dreamylost
+
+/**
+  * 117. 填充每个节点的下一个右侧节点指针 II
+  *
+  * 填充它的每个 next 指针，让这个指针指向其下一个右侧节点。如果找不到下一个右侧节点，则将 next 指针设置为 NULL。
+  *
+  * 初始状态下，所有 next 指针都被设置为 NULL。
+  *
+  * @author 梦境迷离 dreamylost
+  * @since 2020-07-13
+  * @version v1.0
+  */
+object Leetcode_117 extends App {
+
+  val ret = connect(Node.getNode_7())
+  println(ret)
+
+  /**
+    * 层序遍历链接每一层
+    *
+    * 递归与116类似，区别：不是完全二叉树
+    *
+    * 636 ms,20.00%
+    * 52.9 MB,100.00%
+    *
+    * @param root
+    * @return
+    */
+  def connect(root: Node): Node = {
+    if (root == null) return null
+    var queue = Seq[Node]()
+    queue = queue ++ Seq(root)
+    while (queue.nonEmpty) {
+      val size = queue.size
+      for (i <- 0 until size) {
+        val node = queue.head
+        queue = queue.tail
+        //确保只在当前层级结束时才建立下一个指针
+        if (i < size - 1) {
+          node.next = queue.head
+        }
+
+        if (node.left != null) queue = queue ++ Seq(node.left)
+        if (node.right != null) queue = queue ++ Seq(node.right)
+      }
+    }
+
+    root
+  }
+
+  /**
+    * 不使用队列，把每层都看成列表
+    *
+    * 556 ms,80.00%
+    * 53.2 MB,100.00%
+    *
+    * @param root
+    * @return
+    */
+  def connect2(root: Node) = {
+    var head: Node = root
+    while (head != null) {
+      //链表头
+      val level = new Node(Int.MinValue)
+      var tail = level
+      while (head != null) {
+        if (head.left != null) {
+          tail.next = head.left
+          tail = tail.next
+        }
+        if (head.right != null) {
+          tail.next = head.right
+          tail = tail.next
+        }
+        head = head.next
+      }
+      //每次head都从链表头开始
+      head = level.next
+    }
+    root
+  }
+
+}