java集合：二叉树

• 二叉树结点

// Class for storing a single node of a binary tree of intspublic class IntTreeNode {    public int data;    public IntTreeNode left;    public IntTreeNode right;    // constructs a leaf node with given data    public IntTreeNode(int data) {        this(data, null, null);    }    // constructs a branch node with given data, left subtree,    // right subtree    public IntTreeNode(int data, IntTreeNode left,                        IntTreeNode right) {        this.data = data;        this.left = left;        this.right = right;    }}

• 二叉树

public class IntTree {    private IntTreeNode overallRoot;    // pre : max > 0    // post: constructs a sequential tree with given number of    //       nodes    public IntTree(int max) {        if (max <= 0) {            throw new IllegalArgumentException("max: " + max);        }        overallRoot = buildTree(1, max);    }    // post: returns a sequential tree with n as its root unless    //       n is greater than max, in which case it returns an    //       empty tree    private IntTreeNode buildTree(int n, int max) {        if (n > max) {            return null;        } else {            return new IntTreeNode(n, buildTree(2 * n, max),                                   buildTree(2 * n + 1, max));        }    }    // post: prints the tree contents using a preorder traversal    public void printPreorder() {        System.out.print("preorder:");        printPreorder(overallRoot);        System.out.println();    }    // post: prints the tree contents using a preorder traversal    // post: prints in preorder the tree with given root    private void printPreorder(IntTreeNode root) {        if (root != null) {            System.out.print(" " + root.data);            printPreorder(root.left);            printPreorder(root.right);        }    }    // post: prints the tree contents using a inorder traversal    public void printInorder() {        System.out.print("inorder:");        printInorder(overallRoot);        System.out.println();    }    // post: prints in inorder the tree with given root    private void printInorder(IntTreeNode root) {        if (root != null) {            printInorder(root.left);            System.out.print(" " + root.data);            printInorder(root.right);        }    }    // post: prints the tree contents using a postorder traversal    public void printPostorder() {        System.out.print("postorder:");        printPostorder(overallRoot);        System.out.println();    }    // post: prints in postorder the tree with given root    private void printPostorder(IntTreeNode root) {        if (root != null) {            printPostorder(root.left);            printPostorder(root.right);            System.out.print(" " + root.data);        }    }    // post: prints the tree contents, one per line, following an    //       inorder traversal and using indentation to indicate    //       node depth; prints right to left so that it looks    //       correct when the output is rotated.    public void printSideways() {        printSideways(overallRoot, 0);    }    // post: prints in reversed preorder the tree with given    //       root, indenting each line to the given level    private void printSideways(IntTreeNode root, int level) {        if (root != null) {            printSideways(root.right, level + 1);            for (int i = 0; i < level; i++) {                System.out.print("    ");            }            System.out.println(root.data);            printSideways(root.left, level + 1);        }    }}