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Commit 71865c1

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Merge pull request youngyangyang04#1351 from wzqwtt/tree02
添加(二叉树的统一迭代法、102.二叉树的层序遍历、107.二叉树的层次遍历II)Scala版本
2 parents da137a1 + edbb487 commit 71865c1

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‎problems/0102.二叉树的层序遍历.md‎

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@@ -318,6 +318,31 @@ func levelOrder(_ root: TreeNode?) -> [[Int]] {
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return result
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}
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```
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Scala:
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```scala
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// 102.二叉树的层序遍历
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object Solution {
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import scala.collection.mutable
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def levelOrder(root: TreeNode): List[List[Int]] = {
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val res = mutable.ListBuffer[List[Int]]()
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if (root == null) return res.toList
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val queue = mutable.Queue[TreeNode]() // 声明一个队列
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queue.enqueue(root) // 把根节点加入queue
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while (!queue.isEmpty) {
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val tmp = mutable.ListBuffer[Int]()
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val len = queue.size // 求出len的长度
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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
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val curNode = queue.dequeue()
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tmp.append(curNode.value)
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if (curNode.left != null) queue.enqueue(curNode.left)
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if (curNode.right != null) queue.enqueue(curNode.right)
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}
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res.append(tmp.toList)
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}
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res.toList
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}
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}
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```
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Rust:
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@@ -578,6 +603,32 @@ func levelOrderBottom(_ root: TreeNode?) -> [[Int]] {
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}
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```
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Scala:
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```scala
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// 107.二叉树的层次遍历II
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object Solution {
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import scala.collection.mutable
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def levelOrderBottom(root: TreeNode): List[List[Int]] = {
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val res = mutable.ListBuffer[List[Int]]()
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if (root == null) return res.toList
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val queue = mutable.Queue[TreeNode]()
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queue.enqueue(root)
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while (!queue.isEmpty) {
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val tmp = mutable.ListBuffer[Int]()
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val len = queue.size
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for (i <- 0 until len) {
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val curNode = queue.dequeue()
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tmp.append(curNode.value)
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if (curNode.left != null) queue.enqueue(curNode.left)
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if (curNode.right != null) queue.enqueue(curNode.right)
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}
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res.append(tmp.toList)
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}
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// 最后翻转一下
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res.reverse.toList
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}
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Rust:
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```rust

‎problems/二叉树的统一迭代法.md‎

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@@ -591,6 +591,80 @@ function postorderTraversal(root: TreeNode | null): number[] {
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return res;
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};
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```
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Scala:
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```scala
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// 前序遍历
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object Solution {
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import scala.collection.mutable
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def preorderTraversal(root: TreeNode): List[Int] = {
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val res = mutable.ListBuffer[Int]()
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val stack = mutable.Stack[TreeNode]()
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if (root != null) stack.push(root)
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while (!stack.isEmpty) {
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var curNode = stack.top
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if (curNode != null) {
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stack.pop()
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if (curNode.right != null) stack.push(curNode.right)
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if (curNode.left != null) stack.push(curNode.left)
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stack.push(curNode)
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stack.push(null)
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} else {
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stack.pop()
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res.append(stack.pop().value)
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}
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}
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res.toList
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}
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}
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// 中序遍历
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object Solution {
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import scala.collection.mutable
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def inorderTraversal(root: TreeNode): List[Int] = {
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val res = mutable.ListBuffer[Int]()
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val stack = mutable.Stack[TreeNode]()
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if (root != null) stack.push(root)
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while (!stack.isEmpty) {
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var curNode = stack.top
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if (curNode != null) {
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stack.pop()
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if (curNode.right != null) stack.push(curNode.right)
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stack.push(curNode)
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stack.push(null)
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if (curNode.left != null) stack.push(curNode.left)
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} else {
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// 等于空的时候好办,弹出这个元素
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stack.pop()
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res.append(stack.pop().value)
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}
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}
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res.toList
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}
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}
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// 后序遍历
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object Solution {
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import scala.collection.mutable
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def postorderTraversal(root: TreeNode): List[Int] = {
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val res = mutable.ListBuffer[Int]()
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val stack = mutable.Stack[TreeNode]()
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if (root != null) stack.push(root)
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while (!stack.isEmpty) {
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var curNode = stack.top
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if (curNode != null) {
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stack.pop()
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stack.push(curNode)
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stack.push(null)
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if (curNode.right != null) stack.push(curNode.right)
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if (curNode.left != null) stack.push(curNode.left)
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} else {
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stack.pop()
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res.append(stack.pop().value)
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}
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}
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res.toList
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}
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}
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```
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

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