如何打印二叉树？

  • Z时代
  • 2024-01-10
  • 分类：问答

如何发送（node.data）SortTree类到TreePrinter然后用于打印树。如何打印二叉树？

import javax.swing.tree.TreeNode; 
public class SortTree { 
static Node root; 
TreePrinter type =new TreePrinter(); 
class Node<A extends Comparable>{ 
int data; 
Node left, right; 
Node(int d) { 
    data = d; 
    left = null; 
right = null; 
} 
} 
Node sortedArrayToBST(int arr[], int start, int end) { 
if (start > end) { 
    return null; 
} 
int mid = (start + end)/2; 
Node node = new Node(arr[mid]); 
node.left = sortedArrayToBST(arr, start, mid - 1); 
node.right = sortedArrayToBST(arr, mid + 1, end);  
return node; 
} 
void preOrder(Node node) { 
if (node == null) { 
    return; 
} 
//System.out.print(node.data + " "); 
preOrder(node.left); 
preOrder(node.right); 
} 
}

这是TreePrinter类：分类为序帮忙送(node.data)到treeprinter类，然后键入树

import java.io.IOException; 
import java.io.OutputStreamWriter; 
public class TreePrinter { 
public static class Node<T extends Comparable<T>> { 
T value; 
Node<T> left, right; 
public void insertToTree(T v) { 
if (value == null) { 
    value = v; 
    return; 
} 
if (v.compareTo(value) < 0) { 
    if (left == null) { 
     left = new Node<T>(); 
    } 
    left.insertToTree(v); 
} else { 
    if (right == null) { 
     right = new Node<T>(); 
    } 
    right.insertToTree(v); 
} 
} 
public void printTree(OutputStreamWriter out) throws IOException { 
if (right != null) { 
    right.printTree(out, true, ""); 
} 
printNodeValue(out); 
if (left != null) { 
    left.printTree(out, false, ""); 
} 
} 
private void printNodeValue(OutputStreamWriter out) throws IOException { 
if (value == null) { 
    out.write("<null>"); 
} else { 
    out.write(value.toString()); 
} 
out.write('\n'); 
} 
private void printTree(OutputStreamWriter out, boolean isRight, String indent) throws IOException { 
if (right != null) { 
    right.printTree(out, true, indent + (isRight ? "  " : " |  ")); 
} 
out.write(indent); 
if (isRight) { 
    out.write("┌"); 
} else { 
    out.write("└"); 
} 
out.write("────"); 
printNodeValue(out); 
if (left != null) { 
    left.printTree(out, false, indent + (isRight ? " |  " : "  ")); 
} 
}}}

节点：

回答：

我建议你实现一个toString，而不是这TreePrinter。

我稍微更改了Node类，将它移到了SortTree之外，导致代码可用于https://github.com/johanwitters/stackoverflow-tree-printer。

节点的实现是在这里：

package com.johanw.stackoverflow.tree; 
import com.johanw.stackoverflow.util.Helper; 
public class Node<A extends Comparable>{ 
    private static int AMOUNT_INDENT = 3; 
    private int data; 
    private Node left, right; 
    public Node(int d) { 
     data = d; 
     left = null; 
     right = null; 
    } 
    public void setLeft(Node left) { 
     this.left = left; 
    } 
    public void setRight(Node right) { 
     this.right = right; 
    } 
    public int getData() { 
     return data; 
    } 
    public Node getLeft() { 
     return left; 
    } 
    public Node getRight() { 
     return right; 
    } 
    public void indent(StringBuilder builder, int indent) { 
     builder.append(Helper.repeat(indent * (AMOUNT_INDENT + 1), " ")); 
    } 
    public void newLine(StringBuilder builder) { 
     builder.append(System.lineSeparator()); 
    } 
    public String toString(int indent) { 
     StringBuilder builder = new StringBuilder(); 
     builder.append(data); 
     newLine(builder); 
     if (left != null) { 
      indent(builder, indent); 
      builder.append("└" + Helper.repeat(AMOUNT_INDENT, "─") + left.toString(indent + 1)); 
     } 
     if (right != null) { 
      indent(builder, indent); 
      builder.append("└" + Helper.repeat(AMOUNT_INDENT, "─") + right.toString(indent + 1)); 
     } 
     return builder.toString(); 
    } 
    @Override 
    public String toString() { 
     return toString(0); 
    } 
}

下面的单元测试给出了给定的树结构的底部输出：

public class TestSortTree { 
    @Test 
    public void test() { 
     Node node = new Node(1); 
     Node left = new Node(2); 
     Node leftLeft = new Node(22); 
     Node leftRight = new Node(23); 
     Node leftRightLeft = new Node(24); 
     left.setLeft(leftLeft); 
     leftRight.setLeft(new Node(39)); 
     left.setRight(leftRight); 
     node.setLeft(left); 
     node.setRight(new Node(3)); 
     System.out.println(node.toString()); 
    } 
}

我希望这有助于

回答：

为了能够得到点头e.data TreePrinter。我将添加以下代码

class TreePrinter<T extends Comparable<T>>{ 
    Node<T extends Comparable<T>> root; 
    public TreePrinter(){ 
     root = new Node<T extends Comparable<T>>(); 
    } 
    public void insertToTree(T v) { 
     root.insertToTree(v); 
    }

现在会很容易打印使用的算法从这个职位的树：

How to print binary tree diagram?

我会通过进行以下修改将数据发送到Node sortedArrayToBST(int arr[], int start, int end)在SortTree

void sortedArrayToBST(int arr[], int start, int end) { 
    if (start > end) { 
     return; 
    } 
    int mid = (start + end)/2; 
    type.insertToTree(arr[mid]); 
    node.left = sortedArrayToBST(arr, start, mid - 1); 
    node.right = sortedArrayToBST(arr, mid + 1, end); 
}

我还没有试过运行此所以可能需要一些调试，但我认为这个基本想法是可靠的。希望这可以帮助！

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