package com.binaryTree;

// 判断二叉树是否为平衡二叉树,
// 平衡二叉树的条件:左右子树的最大高度之差不超过1,左右子树的整体(子树的子树...)都是平衡二叉树
public class IsBalancedTree {

 public static class Node {
 public int value;
 public Node left;
 public Node right;

 public Node(int data) {
 this.value = data;
 }
 }

 public static boolean isBalanced1(Node head) {
 boolean[] ans = new boolean[1];
 ans[0] = true;
 process1(head, ans);
 return ans[0];
 }

 public static int process1(Node head, boolean[] ans) {
 if (!ans[0] || head == null) {
 return -1;
 }
 int leftHeight = process1(head.left, ans);
 int rightHeight = process1(head.right, ans);
 if (Math.abs(leftHeight - rightHeight) > 1) {
 ans[0] = false;
 }
 return Math.max(leftHeight, rightHeight) + 1;
 }

 public static boolean isBalanced2(Node head) {
 return process(head).isBalanced;
 }

 public static class Info {
 public boolean isBalanced;
 public int height;

 public Info(boolean i, int h) {
 isBalanced = i;
 height = h;
 }
 }

 public static Info process(Node x) {
 if (x == null) {
 return new Info(true, 0);
 }
 Info leftInfo = process(x.left);
 Info rightInfo = process(x.right);
 int height = Math.max(leftInfo.height, rightInfo.height) + 1;
 boolean isBalanced = true;
 if (!leftInfo.isBalanced) {
 isBalanced = false;
 }
 if (!rightInfo.isBalanced) {
 isBalanced = false;
 }
 if (Math.abs(leftInfo.height - rightInfo.height) > 1) {
 isBalanced = false;
 }
 return new Info(isBalanced, height);
 }


 // for test
 public static Node generateRandomBST(int maxLevel, int maxValue) {
 return generate(1, maxLevel, maxValue);
 }

 // for test
 public static Node generate(int level, int maxLevel, int maxValue) {
 if (level > maxLevel || Math.random() < 0.5) {
 return null;
 }
 Node head = new Node((int) (Math.random() * maxValue));
 head.left = generate(level + 1, maxLevel, maxValue);
 head.right = generate(level + 1, maxLevel, maxValue);
 return head;
 }

 public static void main(String[] args) {
 int maxLevel = 5;
 int maxValue = 100;
 int testTimes = 1000000;
 for (int i = 0; i < testTimes; i++) {
 Node head = generateRandomBST(maxLevel, maxValue);
 if (isBalanced1(head) != isBalanced2(head)) {
 System.out.println("Oops!");
 }
 }
 System.out.println("finish!");
 }

}