构建二叉树、二叉树的深度、广度优先遍历

根据数组构建二叉树,并深度、广度优先遍历二叉树:

import java.util.ArrayDeque;

public class BinaryTree {

    static class TreeNode {
        int value;
        TreeNode left;
        TreeNode right;

        public TreeNode(int value) {
            this.value = value;
        }
    }

    TreeNode root;

    public BinaryTree(int[] array) {
        root = makeBinaryTreeByArray(array, 1);
    }

    /** * 采用递归的方式创建一颗二叉树 * 传入的是二叉树的数组表示法 * 构造后是二叉树的二叉链表表示法 */
    public static TreeNode makeBinaryTreeByArray(int[] array, int index) {
        if (index < array.length) {
            int value = array[index];
            if (value != 0) {
                TreeNode t = new TreeNode(value);
                array[index] = 0;
                t.left = makeBinaryTreeByArray(array, index * 2);
                t.right = makeBinaryTreeByArray(array, index * 2 + 1);
                return t;
            }
        }
        return null;
    }

    /** * 深度优先遍历,相当于先根遍历 * 采用非递归实现 * 需要辅助数据结构:栈 */
    public void depthOrderTraversal() {
        if (root == null) {
            System.out.println("empty tree");
            return;
        }
        ArrayDeque<TreeNode> stack = new ArrayDeque<TreeNode>();
        stack.push(root);
        while (stack.isEmpty() == false) {
            TreeNode node = stack.pop();
            System.out.print(node.value + " ");
            if (node.right != null) {
                stack.push(node.right);
            }
            if (node.left != null) {
                stack.push(node.left);
            }
        }
        System.out.print("\n");
    }

    /** * 广度优先遍历 * 采用非递归实现 * 需要辅助数据结构:队列 */
    public void levelOrderTraversal() {
        if (root == null) {
            System.out.println("empty tree");
            return;
        }
        ArrayDeque<TreeNode> queue = new ArrayDeque<TreeNode>();
        queue.add(root);
        while (queue.isEmpty() == false) {
            TreeNode node = queue.remove();
            System.out.print(node.value + " ");
            if (node.left != null) {
                queue.add(node.left);
            }
            if (node.right != null) {
                queue.add(node.right);
            }
        }
        System.out.print("\n");
    }

    /** * 13 * / \ * 65 5 * / \ \ * 97 25 37 * / /\ / * 22 4 28 32 */
    public static void main(String[] args) {
        int[] arr = { 0, 13, 65, 5, 97, 25, 0, 37, 22, 0, 4, 28, 0, 0, 32, 0 };
        BinaryTree tree = new BinaryTree(arr);
        tree.depthOrderTraversal(); // 深度遍历
        tree.levelOrderTraversal(); // 广度遍历
    }

}
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