《程序员代码面试指南》第三章 二叉树问题 找到二叉树中最大搜索二叉树

题目

找到二叉树中最大搜索二叉树

java代码

package com.lizhouwei.chapter3;

/**
 * @Description:找到二叉树中最大搜索二叉树
 * @Author: lizhouwei
 * @CreateDate: 2018/4/14 20:39
 * @Modify by:
 * @ModifyDate:
 */
public class Chapter3_7 {
    public Node biggestSubBST(Node head) {
        int[] record = new int[3];
        return postOrder(head, record);
    }

    public Node postOrder(Node head, int[] record) {
        if (head == null) {
            record[0] = 0;
            record[1] = Integer.MAX_VALUE;//子树最小值
            record[2] = Integer.MIN_VALUE;//子树最大值
            return null;
        }
        int value = head.value;
        Node left = postOrder(head.left, record);
        int leftSize = record[0];
        int leftMin = record[1];
        int leftMax = record[2];
        Node right = postOrder(head.right, record);
        int rightSize = record[0];
        int rightMin = record[1];
        int rightMax = record[2];
        record[1] = Math.min(leftMin, value);
        record[2] = Math.max(rightMax, value);
        if (left == head.left && right == head.right && leftMax < value && value < rightMin) {
            record[0] = leftSize + rightSize + 1;
            return head;
        }
        record[0] = Math.max(leftSize, rightSize);
        return leftSize > rightSize ? left : right;
    }

    //测试
    public static void main(String[] args) {
        Chapter3_7 chapter = new Chapter3_7();
        Node head = new Node(6);
        head.left = new Node(1);
        head.right = new Node(12);
        head.left.left = new Node(0);
        head.left.right = new Node(3);

        head.right.left = new Node(10);
        head.right.right = new Node(13);

        head.right.left.left = new Node(4);
        head.right.left.right = new Node(14);
        head.right.right.left = new Node(20);
        head.right.right.right = new Node(16);

        head.right.left.left.left = new Node(2);
        head.right.left.left.right = new Node(5);
        head.right.left.right.left = new Node(11);
        head.right.left.right.right = new Node(15);
        Node subHead = chapter.biggestSubBST(head);
        NodeUtil.inOrder(subHead);
    }
}