用java用二叉链表表示树，结点的值为结点的序号，创建n个结点的完全二叉树，输出前、中、后三种遍历

以下是Java代码实现：

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    public TreeNode(int x) {
        val = x;
    }
}

class BinaryTree {
    private TreeNode root;
    public BinaryTree(int n) {
        root = createTree(1, n);
    }
    private TreeNode createTree(int i, int n) {
        if (i > n) {
            return null;
        }
        TreeNode root = new TreeNode(i);
        root.left = createTree(i * 2, n);
        root.right = createTree(i * 2 + 1, n);
        return root;
    }
    public void preOrderTraversal() {
        preOrderTraversal(root);
        System.out.println();
    }
    private void preOrderTraversal(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.print(root.val + " ");
        preOrderTraversal(root.left);
        preOrderTraversal(root.right);
    }
    public void inOrderTraversal() {
        inOrderTraversal(root);
        System.out.println();
    }
    private void inOrderTraversal(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrderTraversal(root.left);
        System.out.print(root.val + " ");
        inOrderTraversal(root.right);
    }
    public void postOrderTraversal() {
        postOrderTraversal(root);
        System.out.println();
    }
    private void postOrderTraversal(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrderTraversal(root.left);
        postOrderTraversal(root.right);
        System.out.print(root.val + " ");
    }
}

public class Main {
    public static void main(String[] args) {
        int n = 7;
        BinaryTree binaryTree = new BinaryTree(n);
        System.out.print("前序遍历：");
        binaryTree.preOrderTraversal();
        System.out.print("中序遍历：");
        binaryTree.inOrderTraversal();
        System.out.print("后序遍历：");
        binaryTree.postOrderTraversal();
    }
}

输出结果为：

前序遍历：1 2 4 5 3 6 7 
中序遍历：4 2 5 1 6 3 7 
后序遍历：4 5 2 6 7 3 1