Question

我似乎在向左节点添加正确节点时遇到问题。我有一个预订

中列出的输入文件（.txt）

Fred    1900
2
John    1925
3
Mary    1950
2
Jason   1972
0
Heather 1975
2
Sydney  2002
0
Hailey  2005
0
John    1951
1
Amy 1983
0
Fred    1953
3
Mark    1977
0
Sarah   1979
1
Michael 2005
0
Adam    1982
0
Joan    1927
2
Susan   1949
0
David   1952
1
Fred    1980
0

这是我的Node类：

public class Node {
    public String name;
    public int year;
    //this will help with determining the parent in the insertion process
    public int children;    
    public Node parent;
    public Node left;
    public Node right;


    public Node(String name, int year, int children){
        this.name = name;
        this.year = year;
        this.children = children;
    }
}

假设我的节点创建成功，我似乎在创建实际树时出现问题。

public class FamilyTree {    

    public Node familyTree;

    private Node pivotalNode;
    private Node parent;
    private int children = 0;
    //This method adds a family member to the family tree    
    public void add(Node newNode){
        familyTree = add(familyTree,newNode);
    }
    private Node add(Node familyTree, Node newNode){        
        if(familyTree == null){
            children = newNode.children;
            newNode.parent = parent;
            familyTree = newNode;

        }
        else if(children > 0){
            parent = familyTree;
            familyTree.left = add(familyTree.left, newNode);
            pivotalNode = familyTree.left;
        }
        else if(children == 0){          

            familyTree.right = add(familyTree.right, newNode);
            return pivotalNode;
        }        
        return familyTree;
    }  
}

结果将显示树如下：

这是我的主要方法：

public class Operations {

    //Not necessary but it helps me to get more organized. Just want to extract information first.
    public static ArrayList<String> information = new ArrayList<String>();  

    public static void main(String args[]){
        //extract information from file
        getFileContents();

        //Object initialization
        FamilyTree family = new FamilyTree();

        //some useful variables for loop below
        int children =0;
        String[] splitted = null;
        Node member = null;        

        for(int i=0; i<information.size(); i++){
            //Every other line in the text file perform a different operation
            if(i % 2 == 1){
                try{
                    children = Integer.parseInt(information.get(i));
                    member = new Node(splitted[0], Integer.parseInt(splitted[1]), children);
                    family.add(member);
                }
                catch(Exception e){
                    //this determines if the pattern is broken
                    break;
                }
            }
            if(i % 2 == 0){                               
                splitted = information.get(i).split("\\s+");
                //this determines a pattern difference                
                if(splitted.length < 2){
                    break;
                }
            }
        }
        System.out.print("hi");
    }
    //Pretty self explanatory. Read each line of the file and store it into an array. 
    //Not necessary as everything could technically be done at once (insertion), but this keeps me 
    //more organized to put everything together later on 
    public static void getFileContents(){
        try{
            BufferedReader br = new BufferedReader(new FileReader("includes\\assn2in.txt"));            

            String line;
            String info;

            while ((line = br.readLine()) != null) {
                info = line.replaceAll("\\s+", " ");
                information.add(info);               
            }            
            br.close();


        }
        catch(IOException e){
            System.out.println("Error: "+e);
        }
    } 
}

感谢任何帮助。

Answer 1

你遇到的一个大问题是你的Node类建模二叉树结构 - 也就是说，它包含代表孩子的left和right成员 - 但数据本身不符合这种结构。如果查看图表，您可以看到一些节点有多达三个子节点（例如John 1925和Fred 1953）。您需要使用ArrayList代替left和right，以便Node可以处理任意数量的子项：

public class Node {
    public String name;
    public int year;
    //this will help with determining the parent in the insertion process
    public int expectedNumberOfChildren;    
    public Node parent;
    public ArrayList<Node> children;

    public Node(String name, int year, int expectedNumberOfChildren){
        this.name = name;
        this.year = year;
        this.expectedNumberOfChildren = expectedNumberOfChildren;
        this.children = new ArrayList<Node>(expectedNumberOfChildren);
    }
}

至于从数据文件构建树，我会使用Stack结构和以下算法（伪代码）：

创建一个空堆栈。
初始化一个名为＆＃34; root＆＃34;的Node变量。为null。
打开数据文件以供阅读。
虽然不在文件的末尾：
- 从文件中读取下一个名字，年份和预期的孩子数。
- 从名称，年份和预期的子女数量创建新节点。
- 如果根节点为空：
  - 将根节点设置为新节点。
  - 将新节点推入堆栈。
- 否则：
  - 将最后一个节点弹出堆栈（调用此＆＃34;父级＆＃34;）。
  - 将新节点的父节点设置为刚刚从堆栈弹出的父节点。
  - 将新节点添加到父级的子列表中。
  - 如果父母的孩子列表的实际大小小于父母最初从该文件中读取的孩子的预期孩子数，请将父母推回到堆栈中。
  - 如果新节点的预期子节点数大于零，则将其推入堆栈。
关闭文件。

就是这样。当循环结束时，＆＃34; root＆＃34;假设输入文件格式正确，节点将指向完全构造的树。（之后不再需要堆栈。）

预订遍历树

1 个答案: