如何在Java二叉樹中實現泛型有序遍歷？

Question

如何為二叉樹類創建有序遍歷。 我已經看過並嘗試了其他示例，但似乎無法為我工作。

以下是到目前為止我的有序遍歷方法：

public void inOrder(TreeNode<T> root) {
    if(root !=  null) {
        inOrder(root.left());
        //Visit the node by Printing the node data  
        System.out.printf("%d ",root.value());
        inOrder(root.right());
    }
}

public static void main(String[] args) {
    BinaryTree<Integer> tree = new BinaryTree<Integer>();
    tree.insert(1);
    tree.insert(2);
    tree.insert(3);
    tree.insert(4);
    tree.insert(5);

    inOrder(tree.root);
}

但是我似乎正在錯誤地指出The method inOrder(TreeNode<T>) in the type BinaryTree<T> is not applicable for the arguments (BTree<T>) 。

以下是我的課程： 二叉樹課程

public class BinaryTree<T extends Comparable<? super T>> implements BTree<T> {

    private TreeNode<T> root;

    /**
     * Insert method. Insert a value in the binary tree.
     */
    @Override
    public void insert(T value) {
        if(root == null) { //if tree is empty insert value at root
            root = new TreeNode<T>(value);
        }else if(value.compareTo(value()) < 0) { //insert value to left as its smaller than the root value
            root.left().insert(value);
        }else{ //insert value to right as its greater than the root value
            root.right().insert(value);
        }

    }

    /**
     * Returns the value of a node in the tree.
     */
    @Override
    public T value() {
        return root.value();
    }

    /**
     * Returns the left node in the tree.
     */
    @Override
    public BTree<T> left() {
        return root.left();
    }

    /**
     * Returns the right node in the tree.
     */
    @Override
    public BTree<T> right() {
        return root.right();    
    }
}

TreeNode類

public class TreeNode<T extends Comparable<? super T>> {
    T value;
    BTree<T> left, right;

    public TreeNode(T value) {
        this.value = value;
        left = new BinaryTree<T>();
        right = new BinaryTree<T>();
    }

    public T value() {
        return value;
    }

    public BTree<T> left() {
        return left;
    }

    public BTree<T> right() {
        return right;
    }
}

二叉樹接口

public interface BTree<T extends Comparable<? super T>> {
    public void insert(T value);

    public T value();

    public BTree<T> left();

    public BTree<T> right();

}

Answer 1

您的問題是，在遞歸調用inOrder inOrder()函數時，您傳遞的是BTree對象而不是預期的TreeNode對象：

public void inOrder(TreeNode<T> root) {
    if(root !=  null) {
        inOrder(root.left()); //Passing in a BTree<T> object instead of TreeNode<T> 
        System.out.printf("%d ",root.value());
        inOrder(root.right()); //Passing in a BTree<T> object instead of TreeNode<T>
    }
}

您應該決定還是將存儲在TreeNode對象中的左/右值也用作TreeNode類型，或者在inOrder()函數中將訪問左/右值的結果inOrder()為TreeNode對象。