代码如下:
package AVLTree;import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;public class AVLTree {private class TreeNode{private int data;TreeNode left;TreeNode right;private int height;public TreeNode(int e){data = e;left = null;right = null;height = 0;}}private TreeNode AVLTreeRoot;public AVLTree(){AVLTreeRoot = null;}public int heightTree(TreeNode root){if (root==null) return 0;int l = heightTree(root.left);int r = heightTree(root.right);return (l>r?l:r)+1;}private TreeNode singleLeftRotation(TreeNode root){TreeNode p = root.left;root.left = p.right;p.right = root;root.height = heightTree(root);p.height = heightTree(p);return p;}private TreeNode singleRightRotation(TreeNode root){TreeNode p = root.right;root.right = p.left;p.left = root;root.height = heightTree(root);p.height = heightTree(p);return p;}private TreeNode doubleLeftRightRotation(TreeNode root){root.left = singleRightRotation(root.left);return singleLeftRotation(root);}private TreeNode doubleRightLeftRotation(TreeNode root){root.right = singleLeftRotation(root.right);return singleRightRotation(root);}public TreeNode insertTree(int e,TreeNode root){if (root==null){root = new TreeNode(e);}else if (e < root.data){root.left = insertTree(e,root.left);if (heightTree(root.left)-heightTree(root.right)==2){if (e < root.left.data){root = singleLeftRotation(root);}else{root = doubleLeftRightRotation(root);}}}else if (e > root.data){root.right = insertTree(e,root.right);if (heightTree(root.left)-heightTree(root.right)==-2){if (e > root.right.data){root = singleRightRotation(root);}else{root = doubleRightLeftRotation(root);}}}root.height = heightTree(root);return root;}public boolean createTree(int n){Scanner sc = new Scanner(System.in);for (int i = 0;i<n;i++){int val = sc.nextInt();AVLTreeRoot = insertTree(val,AVLTreeRoot);}return true;}public void levelOrder(){ArrayList<Integer> arrays = new ArrayList<>();Queue<TreeNode> q = new LinkedList<>();if (AVLTreeRoot==null){System.out.println(arrays);return ;}q.add(AVLTreeRoot);while(!q.isEmpty()){TreeNode t = q.poll();arrays.add(t.data);if (t.left!=null) q.add(t.left);if (t.right!=null) q.add(t.right);}System.out.println(arrays);}}测试类如下:
package AVLTree;public class TestAVLTree {public static void main(String[] args){AVLTree bt = new AVLTree();bt.createTree(8);bt.levelOrder();}
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时间的非递归的过程，将该树每个结点的关键字输出（算法导论第三版第十章10.4-5）)
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