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!");
    }

}