add scala #1339

scala-leetcode/README.md

@@ -64,6 +64,7 @@ Leetcode Scala 实现
 * [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)
+* [分裂二叉树的最大乘积](./src/main/scala/io/github/dreamylost/Leetcode_1339.scala)
 
 ## 链表
 

scala-leetcode/src/main/scala/io/github/dreamylost/Leetcode_1339.scala

+/* Licensed under Apache-2.0 @梦境迷离 */
+package io.github.dreamylost
+
+/**
+  * 1339. 分裂二叉树的最大乘积
+  *
+  * 给你一棵二叉树，它的根为 root 。请你删除 1 条边，使二叉树分裂成两棵子树，且它们子树和的乘积尽可能大。
+  *
+  * 由于答案可能会很大，请你将结果对 [[10^9 + 7]] 取模后再返回
+  *
+  * @see https://github.com/jxnu-liguobin
+  * @author 梦境迷离 dreamylost
+  * @version 1.0,2020/7/14
+  */
+object Leetcode_1339 extends App {
+
+  val ret = maxProduct(TreeNodeData.treeData6_1())
+  println(ret)
+
+  /**
+    * 2592 ms,100.00%
+    * 71.5 MB,100.00%
+    *
+    * @param root
+    * @return
+    */
+  def maxProduct(root: TreeNode): Int = {
+    //设，以节点N与上层的边为待删除的边，乘积 = f(N上) * f(N下)，分别为N上，与N下，其中N下的子树是以N为root节点的，另外一半子树比较麻烦，可以使用 sum - f(N下)
+    //即f(N上) = sum - f(N下)
+    //所以子树乘积　＝　sum - f(N下)　×  f(N下)
+    //其中，f(N下)比较好算，就是以当前节点为root节点的子树和，而sum更好算，就是整个树的和
+    //ret = max(ret, sum - f(N下) * f(N下))
+
+    if (root == null) return 0
+    var ret = Long.MinValue
+
+    def sum(r: TreeNode): Int = {
+      if (r == null) return 0
+      r.value + sum(r.left) + sum(r.right)
+    }
+
+    val allNodeSum = sum(root)
+
+    //必须Long
+    def dfs(r: TreeNode): Long = {
+      if (r == null) return 0
+      val cNodeSum = dfs(r.left) + dfs(r.right) + r.value
+      ret = math.max(ret, (allNodeSum - cNodeSum) * cNodeSum)
+      cNodeSum
+    }
+
+    dfs(root)
+
+    (ret % (1e9 + 7)).toInt
+  }
+}

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

@@ -94,6 +94,25 @@ object TreeNodeData {
     n1
   }
 
+  def treeData6_1(): TreeNode = {
+    val n1 = new TreeNode(1)
+    val n2 = new TreeNode(2)
+    val n3 = new TreeNode(3)
+    val n4 = new TreeNode(4)
+    val n5 = new TreeNode(5)
+    val n6 = new TreeNode(6)
+
+    n1.left = n2
+    n1.right = n3
+
+    n2.left = n4
+    n2.right = n5
+
+    n3.left = n6
+
+    n1
+  }
+
   def treeData11(): TreeNode = {
     val treeNode5 = new TreeNode(5)
     val treeNode4 = new TreeNode(4)