From 648014b28a54e953d335e822d7e7a5f98a82e3ea Mon Sep 17 00:00:00 2001 From: ZongqinWang <1722249371@qq.com> Date: Thu, 19 May 2022 10:19:22 +0800 Subject: [PATCH 1/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E7=BB=9F=E4=B8=80=E8=BF=AD=E4=BB=A3=E6=B3=95?= =?UTF-8?q?.md=20Scala=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的统一迭代法.md | 74 +++++++++++++++++++++++++ 1 file changed, 74 insertions(+) diff --git a/problems/二叉树的统一迭代法.md b/problems/二叉树的统一迭代法.md index f6edf586..9ca6ac39 100644 --- a/problems/二叉树的统一迭代法.md +++ b/problems/二叉树的统一迭代法.md @@ -591,6 +591,80 @@ function postorderTraversal(root: TreeNode | null): number[] { return res; }; ``` +Scala: +```scala +// 前序遍历 +object Solution { + import scala.collection.mutable + def preorderTraversal(root: TreeNode): List[Int] = { + val res = mutable.ListBuffer[Int]() + val stack = mutable.Stack[TreeNode]() + if (root != null) stack.push(root) + while (!stack.isEmpty) { + var curNode = stack.top + if (curNode != null) { + stack.pop() + if (curNode.right != null) stack.push(curNode.right) + if (curNode.left != null) stack.push(curNode.left) + stack.push(curNode) + stack.push(null) + } else { + stack.pop() + res.append(stack.pop().value) + } + } + res.toList + } +} +// 中序遍历 +object Solution { + import scala.collection.mutable + def inorderTraversal(root: TreeNode): List[Int] = { + val res = mutable.ListBuffer[Int]() + val stack = mutable.Stack[TreeNode]() + if (root != null) stack.push(root) + while (!stack.isEmpty) { + var curNode = stack.top + if (curNode != null) { + stack.pop() + if (curNode.right != null) stack.push(curNode.right) + stack.push(curNode) + stack.push(null) + if (curNode.left != null) stack.push(curNode.left) + } else { + // 等于空的时候好办，弹出这个元素 + stack.pop() + res.append(stack.pop().value) + } + } + res.toList + } +} + +// 后序遍历 +object Solution { + import scala.collection.mutable + def postorderTraversal(root: TreeNode): List[Int] = { + val res = mutable.ListBuffer[Int]() + val stack = mutable.Stack[TreeNode]() + if (root != null) stack.push(root) + while (!stack.isEmpty) { + var curNode = stack.top + if (curNode != null) { + stack.pop() + stack.push(curNode) + stack.push(null) + if (curNode.right != null) stack.push(curNode.right) + if (curNode.left != null) stack.push(curNode.left) + } else { + stack.pop() + res.append(stack.pop().value) + } + } + res.toList + } +} +``` -----------------------
From 33ed3d980eecec6824fb5b9edad83d7b916c4142 Mon Sep 17 00:00:00 2001 From: ZongqinWang <1722249371@qq.com> Date: Thu, 19 May 2022 10:35:55 +0800 Subject: [PATCH 2/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20102.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86=20Scala?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 25 +++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index ab8f2e57..5afce73a 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -298,6 +298,31 @@ func levelOrder(_ root: TreeNode?) -> [[Int]] { return result } ``` +Scala: +```scala +// 102.二叉树的层序遍历 +object Solution { + import scala.collection.mutable + def levelOrder(root: TreeNode): List[List[Int]] = { + val res = mutable.ListBuffer[List[Int]]() + if (root == null) return res.toList + val queue = mutable.Queue[TreeNode]() // 声明一个队列 + queue.enqueue(root) // 把根节点加入queue + while (!queue.isEmpty) { + val tmp = mutable.ListBuffer[Int]() + val len = queue.size // 求出len的长度 + for (i <- 0 until len) { // 从0到当前队列长度的所有节点都加入到结果集 + val curNode = queue.dequeue() + tmp.append(curNode.value) + if (curNode.left != null) queue.enqueue(curNode.left) + if (curNode.right != null) queue.enqueue(curNode.right) + } + res.append(tmp.toList) + } + res.toList + } +} +``` **此时我们就掌握了二叉树的层序遍历了，那么如下九道力扣上的题目，只需要修改模板的两三行代码（不能再多了），便可打倒！** From 04339562c7ce6c46dbd081551e51f36dcaf5fe8d Mon Sep 17 00:00:00 2001 From: ZongqinWang <1722249371@qq.com> Date: Thu, 19 May 2022 10:36:51 +0800 Subject: [PATCH 3/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20107.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E6=AC=A1=E9=81=8D=E5=8E=86II=20Scal?= =?UTF-8?q?a=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 27 +++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index 5afce73a..e707ce27 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -553,6 +553,33 @@ func levelOrderBottom(_ root: TreeNode?) -> [[Int]] { } ``` +Scala: +```scala +// 107.二叉树的层次遍历II +object Solution { + import scala.collection.mutable + def levelOrderBottom(root: TreeNode): List[List[Int]] = { + val res = mutable.ListBuffer[List[Int]]() + if (root == null) return res.toList + val queue = mutable.Queue[TreeNode]() + queue.enqueue(root) + while (!queue.isEmpty) { + val tmp = mutable.ListBuffer[Int]() + val len = queue.size + for (i <- 0 until len) { + val curNode = queue.dequeue() + tmp.append(curNode.value) + if (curNode.left != null) queue.enqueue(curNode.left) + if (curNode.right != null) queue.enqueue(curNode.right) + } + res.append(tmp.toList) + } + // 最后翻转一下 + res.reverse.toList + } +} +``` + # 199.二叉树的右视图 [力扣题目链接](https://leetcode-cn.com/problems/binary-tree-right-side-view/)