我如何在Java中打印一个二叉树，这样输出就像:
4
/ \
2 5
我的节点:
public class Node<A extends Comparable> {
Node<A> left, right;
A data;
public Node(A data){
this.data = data;
}
}
当前回答
在控制台打印:
500
700 300
200 400
简单代码:
public int getHeight()
{
if(rootNode == null) return -1;
return getHeight(rootNode);
}
private int getHeight(Node node)
{
if(node == null) return -1;
return Math.max(getHeight(node.left), getHeight(node.right)) + 1;
}
public void printBinaryTree(Node rootNode)
{
Queue<Node> rootsQueue = new LinkedList<Node>();
Queue<Node> levelQueue = new LinkedList<Node>();
levelQueue.add(rootNode);
int treeHeight = getHeight();
int firstNodeGap;
int internalNodeGap;
int copyinternalNodeGap;
while(true)
{
System.out.println("");
internalNodeGap = (int)(Math.pow(2, treeHeight + 1) -1);
copyinternalNodeGap = internalNodeGap;
firstNodeGap = internalNodeGap/2;
boolean levelFirstNode = true;
while(!levelQueue.isEmpty())
{
internalNodeGap = copyinternalNodeGap;
Node currNode = levelQueue.poll();
if(currNode != null)
{
if(levelFirstNode)
{
while(firstNodeGap > 0)
{
System.out.format("%s", " ");
firstNodeGap--;
}
levelFirstNode =false;
}
else
{
while(internalNodeGap>0)
{
internalNodeGap--;
System.out.format("%s", " ");
}
}
System.out.format("%3d",currNode.data);
rootsQueue.add(currNode);
}
}
--treeHeight;
while(!rootsQueue.isEmpty())
{
Node currNode = rootsQueue.poll();
if(currNode != null)
{
levelQueue.add(currNode.left);
levelQueue.add(currNode.right);
}
}
if(levelQueue.isEmpty()) break;
}
}
其他回答
在控制台打印:
500
700 300
200 400
简单代码:
public int getHeight()
{
if(rootNode == null) return -1;
return getHeight(rootNode);
}
private int getHeight(Node node)
{
if(node == null) return -1;
return Math.max(getHeight(node.left), getHeight(node.right)) + 1;
}
public void printBinaryTree(Node rootNode)
{
Queue<Node> rootsQueue = new LinkedList<Node>();
Queue<Node> levelQueue = new LinkedList<Node>();
levelQueue.add(rootNode);
int treeHeight = getHeight();
int firstNodeGap;
int internalNodeGap;
int copyinternalNodeGap;
while(true)
{
System.out.println("");
internalNodeGap = (int)(Math.pow(2, treeHeight + 1) -1);
copyinternalNodeGap = internalNodeGap;
firstNodeGap = internalNodeGap/2;
boolean levelFirstNode = true;
while(!levelQueue.isEmpty())
{
internalNodeGap = copyinternalNodeGap;
Node currNode = levelQueue.poll();
if(currNode != null)
{
if(levelFirstNode)
{
while(firstNodeGap > 0)
{
System.out.format("%s", " ");
firstNodeGap--;
}
levelFirstNode =false;
}
else
{
while(internalNodeGap>0)
{
internalNodeGap--;
System.out.format("%s", " ");
}
}
System.out.format("%3d",currNode.data);
rootsQueue.add(currNode);
}
}
--treeHeight;
while(!rootsQueue.isEmpty())
{
Node currNode = rootsQueue.poll();
if(currNode != null)
{
levelQueue.add(currNode.left);
levelQueue.add(currNode.right);
}
}
if(levelQueue.isEmpty()) break;
}
}
改编自Vasya Novikov的答案，使其更二进制，并使用StringBuilder提高效率(在Java中将String对象连接在一起通常效率很低)。
public StringBuilder toString(StringBuilder prefix, boolean isTail, StringBuilder sb) {
if(right!=null) {
right.toString(new StringBuilder().append(prefix).append(isTail ? "│ " : " "), false, sb);
}
sb.append(prefix).append(isTail ? "└── " : "┌── ").append(value.toString()).append("\n");
if(left!=null) {
left.toString(new StringBuilder().append(prefix).append(isTail ? " " : "│ "), true, sb);
}
return sb;
}
@Override
public String toString() {
return this.toString(new StringBuilder(), true, new StringBuilder()).toString();
}
输出:
│ ┌── 7
│ ┌── 6
│ │ └── 5
└── 4
│ ┌── 3
└── 2
└── 1
└── 0
我发现VasyaNovikov的答案对于打印大型通用树非常有用，并将其修改为二叉树
代码:
class TreeNode {
Integer data = null;
TreeNode left = null;
TreeNode right = null;
TreeNode(Integer data) {this.data = data;}
public void print() {
print("", this, false);
}
public void print(String prefix, TreeNode n, boolean isLeft) {
if (n != null) {
System.out.println (prefix + (isLeft ? "|-- " : "\\-- ") + n.data);
print(prefix + (isLeft ? "| " : " "), n.left, true);
print(prefix + (isLeft ? "| " : " "), n.right, false);
}
}
}
样例输出:
\-- 7
|-- 3
| |-- 1
| | \-- 2
| \-- 5
| |-- 4
| \-- 6
\-- 11
|-- 9
| |-- 8
| \-- 10
\-- 13
|-- 12
\-- 14
下面是可视化树的另一种方法:将节点保存为xml文件，然后让浏览器显示层次结构:
class treeNode{
int key;
treeNode left;
treeNode right;
public treeNode(int key){
this.key = key;
left = right = null;
}
public void printNode(StringBuilder output, String dir){
output.append("<node key='" + key + "' dir='" + dir + "'>");
if(left != null)
left.printNode(output, "l");
if(right != null)
right.printNode(output, "r");
output.append("</node>");
}
}
class tree{
private treeNode treeRoot;
public tree(int key){
treeRoot = new treeNode(key);
}
public void insert(int key){
insert(treeRoot, key);
}
private treeNode insert(treeNode root, int key){
if(root == null){
treeNode child = new treeNode(key);
return child;
}
if(key < root.key)
root.left = insert(root.left, key);
else if(key > root.key)
root.right = insert(root.right, key);
return root;
}
public void saveTreeAsXml(){
StringBuilder strOutput = new StringBuilder();
strOutput.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
treeRoot.printNode(strOutput, "root");
try {
PrintWriter writer = new PrintWriter("C:/tree.xml", "UTF-8");
writer.write(strOutput.toString());
writer.close();
}
catch (FileNotFoundException e){
}
catch(UnsupportedEncodingException e){
}
}
}
下面是测试它的代码:
tree t = new tree(1);
t.insert(10);
t.insert(5);
t.insert(4);
t.insert(20);
t.insert(40);
t.insert(30);
t.insert(80);
t.insert(60);
t.insert(50);
t.saveTreeAsXml();
输出如下所示:
我需要在我的一个项目中打印一个二叉树，为此我准备了一个java类TreePrinter，其中一个示例输出是:
[+]
/ \
/ \
/ \
/ \
/ \
[*] \
/ \ [-]
[speed] [2] / \
[45] [12]
下面是TreePrinter类和TextNode类的代码。为了打印任何树，你可以用TextNode类创建一个等效的树。
import java.util.ArrayList;
public class TreePrinter {
public TreePrinter(){
}
public static String TreeString(TextNode root){
ArrayList layers = new ArrayList();
ArrayList bottom = new ArrayList();
FillBottom(bottom, root); DrawEdges(root);
int height = GetHeight(root);
for(int i = 0; i s.length()) min = s.length();
if(!n.isEdge) s += "[";
s += n.text;
if(!n.isEdge) s += "]";
layers.set(n.depth, s);
}
StringBuilder sb = new StringBuilder();
for(int i = 0; i temp = new ArrayList();
for(int i = 0; i 0) temp.get(i-1).left = x;
temp.add(x);
}
temp.get(count-1).left = n.left;
n.left.depth = temp.get(count-1).depth+1;
n.left = temp.get(0);
DrawEdges(temp.get(count-1).left);
}
if(n.right != null){
int count = n.right.x - (n.x + n.text.length() + 2);
ArrayList temp = new ArrayList();
for(int i = 0; i 0) temp.get(i-1).right = x;
temp.add(x);
}
temp.get(count-1).right = n.right;
n.right.depth = temp.get(count-1).depth+1;
n.right = temp.get(0);
DrawEdges(temp.get(count-1).right);
}
}
private static void FillBottom(ArrayList bottom, TextNode n){
if(n == null) return;
FillBottom(bottom, n.left);
if(!bottom.isEmpty()){
int i = bottom.size()-1;
while(bottom.get(i).isEdge) i--;
TextNode last = bottom.get(i);
if(!n.isEdge) n.x = last.x + last.text.length() + 3;
}
bottom.add(n);
FillBottom(bottom, n.right);
}
private static boolean isLeaf(TextNode n){
return (n.left == null && n.right == null);
}
private static int GetHeight(TextNode n){
if(n == null) return 0;
int l = GetHeight(n.left);
int r = GetHeight(n.right);
return Math.max(l, r) + 1;
}
}
class TextNode {
public String text;
public TextNode parent, left, right;
public boolean isEdge;
public int x, depth;
public TextNode(String text){
this.text = text;
parent = null; left = null; right = null;
isEdge = false;
x = 0; depth = 0;
}
}
最后，这里是一个打印给定样本的测试类:
public class Test {
public static void main(String[] args){
TextNode root = new TextNode("+");
root.left = new TextNode("*"); root.left.parent = root;
root.right = new TextNode("-"); root.right.parent = root;
root.left.left = new TextNode("speed"); root.left.left.parent = root.left;
root.left.right = new TextNode("2"); root.left.right.parent = root.left;
root.right.left = new TextNode("45"); root.right.left.parent = root.right;
root.right.right = new TextNode("12"); root.right.right.parent = root.right;
System.out.println(TreePrinter.TreeString(root));
}
}
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