add scala leetcode 653

scala-leetcode/README.md

@@ -33,6 +33,7 @@ Leetcode Scala 实现
 * [把二叉搜索树转换为累加树](./src/main/scala/io/github/dreamylost/Leetcode_538.scala)
 * [二叉树的坡度](./src/main/scala/io/github/dreamylost/Leetcode_563.scala)
 * [根据二叉树创建字符串](./src/main/scala/io/github/dreamylost/Leetcode_606.scala)
+* [两数之和 IV - 输入 BST](./src/main/scala/io/github/dreamylost/Leetcode_653.scala)
 
 ## 链表
 

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

@@ -4,6 +4,7 @@ package io.github.dreamylost
 
 import java.util.{ Queue => _ }
 
+//过期，以后使用List
 import scala.collection.immutable.Queue
 import scala.collection.immutable.Stack
 

scala-leetcode/src/main/scala/io/github/dreamylost/Leetcode_653.scala

+package io.github.dreamylost
+
+/**
+  * 653. 两数之和 IV - 输入 BST
+  *
+  * 给定一个二叉搜索树和一个目标结果，如果 BST 中存在两个元素且它们的和等于给定的目标结果，则返回 true。
+  *
+ * @author 梦境迷离 dreamylost
+  * @since 2020-06-15
+  * @version v1.0
+  */
+object Leetcode_653 extends App {
+
+  val ret = findTarget(TreeNodeData.treeData3_4(), 4)
+  println(ret)
+
+  /**
+    * 2060 ms,16.67%
+    * 54.7 MB,100.00%
+    *
+   * @param root
+    * @param k
+    * @return
+    */
+  def findTarget(root: TreeNode, k: Int): Boolean = {
+    def inorderTraversal(root: TreeNode): Seq[Int] = {
+      var ret = Seq[Int]()
+      var stack = List[TreeNode]()
+      if (root == null) return ret
+      var cur = root
+      while (cur != null || stack.nonEmpty) {
+        while (cur != null) {
+          //头进头出模拟栈
+          stack = cur :: stack
+          cur = cur.left
+        }
+        val (node, s) = (stack.head, stack.tail)
+        stack = s
+        ret = ret ++ Seq(node.value)
+        cur = node.right
+      }
+      ret
+    }
+
+    val nums = inorderTraversal(root)
+    var i = 0
+    var j = nums.length - 1
+    while (i < j) {
+      if (nums(i) + nums(j) == k) {
+        return true
+      } else if (nums(i) + nums(j) < k) {
+        i += 1
+      } else {
+        j -= 1
+      }
+    }
+    false
+  }
+
+}