从文件构造二叉树

Question

I have a Binary Tree file formatted like so:

121
00
99
010
120
011
97
10
98
11

Where it's formatted like (ascii val) over (traversal code). 0 = left one, 1 = right one

So the ascii value 121 would be stored in a tree like:

   -1
   /   
 -1       ...
 /
121

How do I construct this properly?

This is how I am doing it currently:

TreeNode root;

public Tree(Scanner input){
    while(input.hasNextLine()){
        int ascii = Integer(input.nextLine());
        String code = input.nextLine();
        root = insert(root, ascii, code);
    }
}

public TreeNode insert(TreeNode node, int ascii, String code){
    if(code == ""){
        return new TreeNode(ascii); //treenode is just data, left right
    }

    if(node == null)
        node = new TreeNode(-1);

    char c = code.charAt(0);

    if(c == '0')
        node.left = insert(node.left, ascii, code.substring(1));
    else if(c == '1')
        node.right = insert(node.right, ascii, code.substring(1));

    return node;
}

I do a preorder print, and it looks right, but when i try to decode a huffman-encoded file it does it wrong. Does anything jump out at you as wrong? I can post my decode stuff, but it is a little tricky because I am using a custom BitInputStream class that is a little too big to post here.

Answer 1

Check if c is really code you are expecting, if it is not you will just return node.

if(c == '0')
    node.left = insert(node.left, ascii, code.substring(1));
else if(c == '1')
    node.right = insert(node.right, ascii, code.substring(1));
else
    throw new IllegalArgumentException();

Answer 2

Perhaps it's because you're trying to compare Strings using the == .

== compares whether the references to the object are equal, while the [stringname].equals(otherstring) method compares whether the contents of the two strings are equal.
For example, you have

String code = "hi";
String other = "hi";
code.equals(other);` 
returns true.