fix scala BTT.scala warnings, add scala leetcode 965

scala-leetcode/README.md

@@ -40,6 +40,7 @@ Leetcode Scala 实现
 * [检查平衡性](./src/main/scala/io/github/dreamylost/Leetcode_Interview_0404.scala)
 * [叶子相似的树](./src/main/scala/io/github/dreamylost/Leetcode_872.scala)
 * [递增顺序查找树](./src/main/scala/io/github/dreamylost/Leetcode_897.scala)
+* [单值二叉树](./src/main/scala/io/github/dreamylost/Leetcode_965.scala)
 
 ## 链表
 

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

@@ -39,34 +39,36 @@ object BTT extends App {
   }
 
   //前，144. Binary Tree Preorder Traversal (Medium)
+  @unchecked
   def preorderTraversal(root: TreeNode): Seq[Int] = {
     var ret = Seq[Int]()
-    var stack = Stack[TreeNode]()
-    stack = stack.push(root)
+    var stack = List[TreeNode]()
+    stack = root :: stack
     while (stack.nonEmpty) {
-      val (node, s) = stack.pop2
+      val (node, s) = stack.head -> stack.tail
       stack = s
       if (node != null) {
         ret = ret ++ Seq(node.value)
-        stack = stack.push(node.right) // 先右后左，保证左子树先遍历
-        stack = stack.push(node.left)
+        stack = node.right :: stack // 先右后左，保证左子树先遍历
+        stack = node.left :: stack
       }
     }
     ret
   }
 
   //中， 94. Binary Tree Inorder Traversal (Medium)
+  @unchecked
   def inorderTraversal(root: TreeNode): Seq[Int] = {
     var ret = Seq[Int]()
-    var stack = Stack[TreeNode]()
+    var stack = List[TreeNode]()
     if (root == null) return ret
     var cur = root
     while (cur != null || stack.nonEmpty) {
       while (cur != null) {
-        stack = stack.push(cur)
+        stack = cur :: stack
         cur = cur.left
       }
-      val (node, s) = stack.pop2
+      val (node, s) = stack.head -> stack.tail
       stack = s
       ret = ret ++ Seq(node.value)
       cur = node.right
@@ -79,17 +81,18 @@ object BTT extends App {
     * 前序遍历为 root -> left -> right，后序遍历为 left -> right -> root。可以修改前序遍历成为 root -> right -> left，那么这个顺序就和后序遍历正好相反。
     */
   //后，145. Binary Tree Postorder Traversal (Medium)
+  @unchecked
   def postorderTraversal(root: TreeNode): Seq[Int] = {
     var ret = Seq[Int]()
-    var stack = Stack[TreeNode]()
-    stack = stack.push(root)
+    var stack = List[TreeNode]()
+    stack = root :: stack
     while (stack.nonEmpty) {
-      val (node, s) = stack.pop2
+      val (node, s) = stack.head -> stack.tail
       stack = s
       if (node != null) {
         ret = ret ++ Seq(node.value)
-        stack = stack.push(node.left) // 先右后左，保证左子树先遍历
-        stack = stack.push(node.right)
+        stack = node.left :: stack // 先右后左，保证左子树先遍历
+        stack = node.right :: stack
       }
     }
     ret.reverse

scala-leetcode/src/main/scala/io/github/dreamylost/Leetcode_501.scala

@@ -55,7 +55,7 @@ object Leetcode_501 extends App {
     var ret = Array[Int]()
 
     def inOrder(root: TreeNode): Unit = {
-      if (root == null) return;
+      if (root == null) return
       inOrder(root.left)
       if (preNode != null && preNode.value == root.value) {
         curCount += 1

scala-leetcode/src/main/scala/io/github/dreamylost/Leetcode_965.scala

+package io.github.dreamylost
+
+/**
+  * 965. 单值二叉树
+  *
+ * 如果二叉树每个节点都具有相同的值，那么该二叉树就是单值二叉树。
+  *
+ * 只有给定的树是单值二叉树时，才返回 true；否则返回 false。
+  *
+ * @author 梦境迷离 dreamylost
+  * @since 2020-06-21
+  * @version v1.0
+  */
+object Leetcode_965 extends App {
+
+  val ret = isUnivalTree(TreeNodeData.treeData3_5())
+  println(ret)
+
+  /**
+    * 记录当前节点的前缀即可
+    * 540 ms,100.00%
+    * 50.8 MB,100.00%
+    *
+   * @param root
+    * @return
+    */
+  def isUnivalTree(root: TreeNode): Boolean = {
+    var ret = true
+    var preNode: TreeNode = null
+
+    def helper(r: TreeNode): Unit = {
+      if (r == null) return
+      helper(r.left)
+      if (preNode != null && preNode.value != r.value) {
+        ret = false
+      }
+      preNode = r
+      helper(r.right)
+    }
+
+    helper(root)
+    ret
+  }
+
+}