Question

import java.util.Scanner;

public class BinaryTree {

private int info;
private BinaryTree left;
private BinaryTree right;
private int sum;

public BinaryTree()
{
    left = null;
    right = null;
}
// This is a second constructor. 
// It can tell the difference by parameter.
public BinaryTree(int theInfo)
{
    Scanner sc = new Scanner(System.in);
    int intNum;
    String s;

    info = theInfo;

    System.out.print("Does the node " + info + " have a left child (y or n)? ");
    s = sc.next();
    if (s.equals("y"))
    {
        System.out.print ("What value should go in the left child node? ");
        intNum = sc.nextInt();
        left = new BinaryTree(intNum);
    }
    System.out.print("Does the node " + info + " have a right child (y or n)? ");
    s = sc.next();
    if (s.equals("y"))
    {
        System.out.print ("What value should go in the right child node? ");
        intNum = sc.nextInt();
        right = new BinaryTree(intNum);
    }
}

public void TraverseNLR()
{

    System.out.print(info + " ");
    if (left != null)
    {
        left.TraverseNLR();
    }
    if (right != null)
    {
        right.TraverseNLR();
    }
}

public void TraverseLNR()
{
    if (left != null)
    {
        left.TraverseLNR();
    }
    System.out.print(info + " ");
    if (right != null)
    {
        right.TraverseLNR();
    }
}

public void TraverseLRN()
{

    if (left != null)
    {
        left.TraverseLRN();
    }
    if (right != null)
    {
        right.TraverseLRN();
    }
    System.out.print(info + " ");
}
/* QUESTION FUNCTION HERE */
public int sumValues()
{ 
    System.out.print(info + " ");
    sum += info;
    if (left != null)
    {
        sum += info;
        left.TraverseNLR();
    }

    if (right != null)
    {
        sum += info;
        right.TraverseNLR();
    }
    return sum;
 }
}

import java.util.Scanner;

public class BinaryTester {

public static void main(String[] args) 
{
    BinaryTree myTree;
    Scanner sc = new Scanner(System.in);
    int intNum;

    System.out.print("What value should go in the root? ");
    intNum = sc.nextInt();
    myTree = new BinaryTree(intNum);
    //myTree.TraverseNLR();
    //System.out.println();
    //myTree.TraverseLNR();
    //System.out.println();
    //myTree.TraverseLRN();
    //System.out.println();
    System.out.println("Sum is " + myTree.sumValues());
    //myTree.sumValues();
  }
}

我无法找到树形图的总和。例如，我将输入：

What value should go in the root? 400
Does the node 400 have a left child (y or n)? y  
What value should go in the left child node? 100
Does the node 100 have a left child (y or n)? n
Does the node 100 have a right child (y or n)? y
What value should go in the right child node? 300
Does the node 300 have a left child (y or n)? n 
Does the node 300 have a right child (y or n)? n 
Does the node 400 have a right child (y or n)? y
What value should go in the right child node? 500
Does the node 500 have a left child (y or n)? n
Does the node 500 have a right child (y or n)? n
400 100 300 500 Sum is 1200

并得到总和是1200而不是真正的答案1300.必须有一些我不能递归理解的东西。怎么可能从总和中跳过100呢？我在全局制作了sum变量，因此它会记住我指定的所有内容。有没有人有任何提示或指向我总结整个Treemap的方向？

Answer 1

我不明白TraverseXXX（）函数的用途是什么。你应该能够摆脱它们，并使用递归重写你的sumValues（）函数：

public int sumValues() {
    System.out.println(info + " ");
    int sum = info; // account for current node

    if (left != null)
        sum += left.sumValues(); // add sum of left subtree

    if (right != null)
        sum += right.sumValues(); // add sum of right subtree

    return sum;
}

将此代码用于sumValues()我得到了正确的输出1300：

What value should go in the root? 400
Does the node 400 have a left child (y or n)? y
What value should go in the left child node? 100
Does the node 100 have a left child (y or n)? n
Does the node 100 have a right child (y or n)? y
What value should go in the right child node? 300
Does the node 300 have a left child (y or n)? n
Does the node 300 have a right child (y or n)? n
Does the node 400 have a right child (y or n)? y
What value should go in the right child node? 500
Does the node 500 have a left child (y or n)? n
Does the node 500 have a right child (y or n)? n
400 
100 
300 
500 
Sum is 1300

如何在树形图中找到总和？ Java的

1 个答案: