Java 树的左视图或右视图
提供树的左/右视图的有效代码是什么 例:-Java 树的左视图或右视图,java,algorithm,tree,logic,Java,Algorithm,Tree,Logic,提供树的左/右视图的有效代码是什么 例:- 1 / \ 左视图-->>47您是对的,具有像 Queue<Node> queue = new ArrayDeque<Node>(); for (Node node = root; node != null; node = queue.poll()) { if (node.leftChild != null) queue.add(node.leftChild); if (node.rightChild !=
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左视图-->>47您是对的,具有像
Queue<Node> queue = new ArrayDeque<Node>();
for (Node node = root; node != null; node = queue.poll()) {
if (node.leftChild != null) queue.add(node.leftChild);
if (node.rightChild != null) queue.add(node.rightChild);
}
Queue Queue=new ArrayDeque();
for(Node=root;Node!=null;Node=queue.poll()){
如果(node.leftChild!=null)queue.add(node.leftChild);
如果(node.rightChild!=null)queue.add(node.rightChild);
}
很难知道一个级别的结束和下一个级别的开始。这可以通过使用两个队列来解决
Queue<Node> currentLevel = new ArrayDeque<Node>();
if (root != null) currentLevel.add(root);
while (true) {
Node node = currentLevel.poll();
if (node == null) break;
/* node is the leftmost on its level */
Queue<Node> nextLevel = new ArrayDeque<Node>();
do {
if (node.leftChild != null) nextLevel.add(node.leftChild);
if (node.rightChild != null) nextLevel.add(node.rightChild);
node = currentLevel.poll();
} while (node != null);
currentLevel = nextLevel;
}
Queue currentLevel=new ArrayDeque();
如果(root!=null)currentLevel.add(root);
while(true){
Node Node=currentLevel.poll();
如果(node==null)中断;
/*节点是其级别上最左侧的节点*/
Queue nextLevel=new ArrayDeque();
做{
如果(node.leftChild!=null)nextLevel.add(node.leftChild);
如果(node.rightChild!=null)nextLevel.add(node.rightChild);
node=currentLevel.poll();
}while(node!=null);
currentLevel=nextLevel;
}
仅使用单个队列获取左(或右)视图并不困难。将最右边的子节点排队后,在队列中插入“null”作为标记,以在执行级别顺序遍历时标记下一个(子)级别的结束
class Node{
Node left, right;
int value;
Node(int value){
left=right=null;
this.value = value;
}
}
public class BinaryTree
{
Node root;
public void leftView(){
//Using single queue.
boolean leftmost = true;
if(this.root == null) return;
Queue<Node> q = new LinkedList<>();
q.add(this.root);
q.add(null);
while(q.isEmpty() == false){
Node rear = q.poll();
if(leftmost == true) {
if(rear == null) break;
System.out.print(rear.value + " ");
leftmost = false;
}
if(rear.left != null) q.add(rear.left);
if(rear.right != null) q.add(rear.right);
if(q.peek() == null) {
leftmost = true;
q.poll(); //remove it from rear
q.add(null); //add it at front.
}
}
//OUTPUT : 12 10 25 50
}
public static void main (String[] args) throws java.lang.Exception
{
BinaryTree bt = new BinaryTree();
bt.root = new Node(12);
bt.root.left = new Node(10);
bt.root.right = new Node(30);
bt.root.right.left = new Node(25);
bt.root.right.left.left = new Node(50);
bt.root.right.right = new Node(40);
// 12
// / \
// 10 30
// / \
// 25 40
// /
// 50
bt.leftView();
}
}
类节点{
左、右淋巴结;
int值;
节点(int值){
左=右=空;
这个值=值;
}
}
公共类二叉树
{
节根;
public void leftView(){
//使用单队列。
布尔最左边=真;
if(this.root==null)返回;
队列q=新的LinkedList();
q、 添加(this.root);
q、 添加(空);
while(q.isEmpty()==false){
节点后部=q.poll();
如果(最左边==真){
如果(后==null)中断;
System.out.print(rear.value+“”);
最左=假;
}
如果(左后!=null)q.add(左后);
如果(右后!=null)q.add(右后);
如果(q.peek()==null){
最左=真;
q、 poll();//将其从后部卸下
q、 add(null);//将其添加到前面。
}
}
//产出:1210250
}
公共静态void main(字符串[]args)引发java.lang.Exception
{
BinaryTree bt=新的BinaryTree();
bt.root=新节点(12);
bt.root.left=新节点(10);
bt.root.right=新节点(30);
bt.root.right.left=新节点(25);
bt.root.right.left.left=新节点(50);
bt.root.right.right=新节点(40);
// 12
// / \
// 10 30
// / \
// 25 40
// /
// 50
bt.leftView();
}
}
打印左视图的算法:
使用全局变量maxLevel跟踪到目前为止覆盖的最大级别
现在,每当我们收到一个高于maxLevel的级别时,我们就会打印该节点的值
我们以预先订购的方式进行打印,这样,如果存在,在右之前打印左
以下是最终代码:
class BinaryTree {
class TreeNode {
int data;
TreeNode left;
TreeNode right;
public TreeNode(int data) {
this.data=data;
}
}
private static int maxLevel = -1;
public static leftView(TreeNode root) {
left_view(root, 0);
}
private static void left_view(BTNode root, int level) {
if (root == null)
return;
if (level > maxLevel) {
System.out.println(root.data);
maxLevel = level;
}
left_view(root.left, level + 1);
left_view(root.right, level + 1);
}
包com.Trees.sumit
导入java.util.LinkedList;
导入java.util.Queue
公共类左视图{
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeNode root = createBinaryTree();
Queue<TreeNode> queue = new LinkedList<>();
System.out.println("Left View" );
queue.add(root);
while (!queue.isEmpty()) {
System.out.println(queue.peek().data);
int queueSize = queue.size();
while (queueSize > 0) {
TreeNode removedNode = queue.poll();
if (removedNode.left != null)
queue.add(removedNode.left);
if (removedNode.right != null)
queue.add(removedNode.right);
queueSize--;
}
}
}
public static class TreeNode {
int data;
TreeNode left;
TreeNode right;
public TreeNode(int data) {
super();
this.data = data;
}
}
private static TreeNode createBinaryTree() {
// TODO Auto-generated method stub
TreeNode rootNode = new TreeNode(40);
TreeNode root20 = new TreeNode(20);
TreeNode root10 = new TreeNode(10);
TreeNode root30 = new TreeNode(30);
TreeNode root50 = new TreeNode(50);
TreeNode root55 = new TreeNode(55);
TreeNode root57 = new TreeNode(57);
TreeNode root60 = new TreeNode(60);
TreeNode root70 = new TreeNode(70);
rootNode.left = root20;
rootNode.right = root60;
root50.right = root55;
root55.right = root57;
root20.left = root10;
root20.right = root30;
root60.left = root50;
root60.right = root70;
return rootNode;
}
publicstaticvoidmain(字符串[]args){
//TODO自动生成的方法存根
TreeNode root=createBinaryTree();
Queue Queue=new LinkedList();
System.out.println(“左视图”);
添加(根);
而(!queue.isEmpty()){
System.out.println(queue.peek().data);
int queueSize=queue.size();
而(队列大小>0){
TreeNode removedNode=queue.poll();
if(removedNode.left!=null)
添加(removedNode.left);
if(removedNode.right!=null)
添加(removedNode.right);
队列大小--;
}
}
}
公共静态类树节点{
int数据;
左树突;
特雷诺德右翼;
公共树节点(int数据){
超级();
这个数据=数据;
}
}
私有静态树节点createBinaryTree(){
//TODO自动生成的方法存根
TreeNode rootNode=新的TreeNode(40);
TreeNode root20=新的TreeNode(20);
TreeNode root10=新的TreeNode(10);
TreeNode root30=新的TreeNode(30);
TreeNode root50=新的TreeNode(50);
TreeNode root55=新的TreeNode(55);
TreeNode root57=新的TreeNode(57);
TreeNode root60=新的TreeNode(60);
TreeNode root70=新的TreeNode(70);
rootNode.left=root20;
rootNode.right=root60;
root50.right=root55;
root55.right=root57;
root20.left=root10;
root20.right=root30;
root60.left=root50;
root60.right=root70;
返回根节点;
}
}无递归
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeNode root = createBinaryTree();
Queue<TreeNode> queue = new LinkedList<>();
System.out.println("Left View" );
queue.add(root);
while (!queue.isEmpty()) {
System.out.println(queue.peek().data);
int queueSize = queue.size();
while (queueSize > 0) {
TreeNode removedNode = queue.poll();
if (removedNode.left != null)
queue.add(removedNode.left);
if (removedNode.right != null)
queue.add(removedNode.right);
queueSize--;
}
}
}
public static class TreeNode {
int data;
TreeNode left;
TreeNode right;
public TreeNode(int data) {
super();
this.data = data;
}
}
private static TreeNode createBinaryTree() {
// TODO Auto-generated method stub
TreeNode rootNode = new TreeNode(40);
TreeNode root20 = new TreeNode(20);
TreeNode root10 = new TreeNode(10);
TreeNode root30 = new TreeNode(30);
TreeNode root50 = new TreeNode(50);
TreeNode root55 = new TreeNode(55);
TreeNode root57 = new TreeNode(57);
TreeNode root60 = new TreeNode(60);
TreeNode root70 = new TreeNode(70);
rootNode.left = root20;
rootNode.right = root60;
root50.right = root55;
root55.right = root57;
root20.left = root10;
root20.right = root30;
root60.left = root50;
root60.right = root70;
return rootNode;
}