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;
}
}
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
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
其他回答
我已经创建了简单的二叉树打印机。您可以随心所欲地使用和修改它,但无论如何它都没有优化。我认为这里有很多东西可以改进;)
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class BTreePrinterTest {
private static Node<Integer> test1() {
Node<Integer> root = new Node<Integer>(2);
Node<Integer> n11 = new Node<Integer>(7);
Node<Integer> n12 = new Node<Integer>(5);
Node<Integer> n21 = new Node<Integer>(2);
Node<Integer> n22 = new Node<Integer>(6);
Node<Integer> n23 = new Node<Integer>(3);
Node<Integer> n24 = new Node<Integer>(6);
Node<Integer> n31 = new Node<Integer>(5);
Node<Integer> n32 = new Node<Integer>(8);
Node<Integer> n33 = new Node<Integer>(4);
Node<Integer> n34 = new Node<Integer>(5);
Node<Integer> n35 = new Node<Integer>(8);
Node<Integer> n36 = new Node<Integer>(4);
Node<Integer> n37 = new Node<Integer>(5);
Node<Integer> n38 = new Node<Integer>(8);
root.left = n11;
root.right = n12;
n11.left = n21;
n11.right = n22;
n12.left = n23;
n12.right = n24;
n21.left = n31;
n21.right = n32;
n22.left = n33;
n22.right = n34;
n23.left = n35;
n23.right = n36;
n24.left = n37;
n24.right = n38;
return root;
}
private static Node<Integer> test2() {
Node<Integer> root = new Node<Integer>(2);
Node<Integer> n11 = new Node<Integer>(7);
Node<Integer> n12 = new Node<Integer>(5);
Node<Integer> n21 = new Node<Integer>(2);
Node<Integer> n22 = new Node<Integer>(6);
Node<Integer> n23 = new Node<Integer>(9);
Node<Integer> n31 = new Node<Integer>(5);
Node<Integer> n32 = new Node<Integer>(8);
Node<Integer> n33 = new Node<Integer>(4);
root.left = n11;
root.right = n12;
n11.left = n21;
n11.right = n22;
n12.right = n23;
n22.left = n31;
n22.right = n32;
n23.left = n33;
return root;
}
public static void main(String[] args) {
BTreePrinter.printNode(test1());
BTreePrinter.printNode(test2());
}
}
class Node<T extends Comparable<?>> {
Node<T> left, right;
T data;
public Node(T data) {
this.data = data;
}
}
class BTreePrinter {
public static <T extends Comparable<?>> void printNode(Node<T> root) {
int maxLevel = BTreePrinter.maxLevel(root);
printNodeInternal(Collections.singletonList(root), 1, maxLevel);
}
private static <T extends Comparable<?>> void printNodeInternal(List<Node<T>> nodes, int level, int maxLevel) {
if (nodes.isEmpty() || BTreePrinter.isAllElementsNull(nodes))
return;
int floor = maxLevel - level;
int endgeLines = (int) Math.pow(2, (Math.max(floor - 1, 0)));
int firstSpaces = (int) Math.pow(2, (floor)) - 1;
int betweenSpaces = (int) Math.pow(2, (floor + 1)) - 1;
BTreePrinter.printWhitespaces(firstSpaces);
List<Node<T>> newNodes = new ArrayList<Node<T>>();
for (Node<T> node : nodes) {
if (node != null) {
System.out.print(node.data);
newNodes.add(node.left);
newNodes.add(node.right);
} else {
newNodes.add(null);
newNodes.add(null);
System.out.print(" ");
}
BTreePrinter.printWhitespaces(betweenSpaces);
}
System.out.println("");
for (int i = 1; i <= endgeLines; i++) {
for (int j = 0; j < nodes.size(); j++) {
BTreePrinter.printWhitespaces(firstSpaces - i);
if (nodes.get(j) == null) {
BTreePrinter.printWhitespaces(endgeLines + endgeLines + i + 1);
continue;
}
if (nodes.get(j).left != null)
System.out.print("/");
else
BTreePrinter.printWhitespaces(1);
BTreePrinter.printWhitespaces(i + i - 1);
if (nodes.get(j).right != null)
System.out.print("\\");
else
BTreePrinter.printWhitespaces(1);
BTreePrinter.printWhitespaces(endgeLines + endgeLines - i);
}
System.out.println("");
}
printNodeInternal(newNodes, level + 1, maxLevel);
}
private static void printWhitespaces(int count) {
for (int i = 0; i < count; i++)
System.out.print(" ");
}
private static <T extends Comparable<?>> int maxLevel(Node<T> node) {
if (node == null)
return 0;
return Math.max(BTreePrinter.maxLevel(node.left), BTreePrinter.maxLevel(node.right)) + 1;
}
private static <T> boolean isAllElementsNull(List<T> list) {
for (Object object : list) {
if (object != null)
return false;
}
return true;
}
}
输出1:
2
/ \
/ \
/ \
/ \
7 5
/ \ / \
/ \ / \
2 6 3 6
/ \ / \ / \ / \
5 8 4 5 8 4 5 8
输出2:
2
/ \
/ \
/ \
/ \
7 5
/ \ \
/ \ \
2 6 9
/ \ /
5 8 4
迈克尔。克鲁兹曼,我不得不说,这人不错。这很有用。
然而,上面的方法只适用于个位数:如果您要使用多个数字,结构将会错位,因为您使用的是空格而不是制表符。
至于我后来的代码,我需要更多的数字,所以我自己编写了一个程序。
它现在有一些bug,现在我感觉很懒去纠正它们,但它打印得非常漂亮,节点可以接受更大数量的数字。
这棵树不会像问题提到的那样,但它旋转了270度:)
public static void printBinaryTree(TreeNode root, int level){
if(root==null)
return;
printBinaryTree(root.right, level+1);
if(level!=0){
for(int i=0;i<level-1;i++)
System.out.print("|\t");
System.out.println("|-------"+root.val);
}
else
System.out.println(root.val);
printBinaryTree(root.left, level+1);
}
将此函数与您自己指定的TreeNode一起放置,并保持初始级别为0,并享受!
以下是一些输出示例:
| | |-------11
| |-------10
| | |-------9
|-------8
| | |-------7
| |-------6
| | |-------5
4
| |-------3
|-------2
| |-------1
| | | |-------10
| | |-------9
| |-------8
| | |-------7
|-------6
| |-------5
4
| |-------3
|-------2
| |-------1
唯一的问题是延伸的分支;我会尽快解决这个问题,但在此之前你也可以使用它。
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));
}
}
这是水平视图最简单的解决方案。我举了很多例子。很适合我的目的。更新自@ ntin -k的回答。
public void print(String prefix, BTNode n, boolean isLeft) {
if (n != null) {
print(prefix + " ", n.right, false);
System.out.println (prefix + ("|-- ") + n.data);
print(prefix + " ", n.left, true);
}
}
电话:
bst.print("", bst.root, false);
解决方案:
|-- 80
|-- 70
|-- 60
|-- 50
|-- 40
|-- 30
|-- 20
|-- 10
根据VasyaNovikov的回答。改进了一些Java魔术:泛型和函数接口。
/**
* Print a tree structure in a pretty ASCII fromat.
* @param prefix Currnet previx. Use "" in initial call!
* @param node The current node. Pass the root node of your tree in initial call.
* @param getChildrenFunc A {@link Function} that returns the children of a given node.
* @param isTail Is node the last of its sibblings. Use true in initial call. (This is needed for pretty printing.)
* @param <T> The type of your nodes. Anything that has a toString can be used.
*/
private <T> void printTreeRec(String prefix, T node, Function<T, List<T>> getChildrenFunc, boolean isTail) {
String nodeName = node.toString();
String nodeConnection = isTail ? "└── " : "├── ";
log.debug(prefix + nodeConnection + nodeName);
List<T> children = getChildrenFunc.apply(node);
for (int i = 0; i < children.size(); i++) {
String newPrefix = prefix + (isTail ? " " : "│ ");
printTreeRec(newPrefix, children.get(i), getChildrenFunc, i == children.size()-1);
}
}
初始调用示例:
Function<ChecksumModel, List<ChecksumModel>> getChildrenFunc = node -> getChildrenOf(node)
printTreeRec("", rootNode, getChildrenFunc, true);
将输出如下内容
└── rootNode
├── childNode1
├── childNode2
│ ├── childNode2.1
│ ├── childNode2.2
│ └── childNode2.3
├── childNode3
└── childNode4