出鞘之剑指offer-第26题 (树的子结构)

题目：

输入两棵二叉树 A 和 B ，判断 B 是不是 A 的子结构。 

分析一：

 使用递归的方式。

代码一：

package offer.xzs.twentyone2thirty.twentysix;

import java.util.Arrays;

public class Demo01 {
    public static void main(String[] args) {
        int[] pre1 = { 8, 8, 9, 2, 4, 7, 7 };
        int[] mid1 = { 9, 8, 4, 2, 7, 8, 7 };
        BinaryTree tree1 = build(pre1, mid1);
        preShow(tree1);
        System.out.println();
        int[] pre2 = { 8, 9, 3 };
        int[] mid2 = { 9, 8, 3 };
        BinaryTree tree2 = build(pre2, mid2);
        preShow(tree2);
        System.out.println();
        boolean result = judgeStructrue(tree1, tree2);
        System.out.println(result);
    }

    public static boolean judgeStructrue(BinaryTree tree1, BinaryTree tree2) {
        if (tree1 == null || tree2 == null) {
            return false;
        }
        return judge(tree1, tree2) || judgeStructrue(tree1.getLeft(), tree2) || judgeStructrue(tree1.getRight(), tree2);
    }

    public static boolean judge(BinaryTree tree1, BinaryTree tree2) {
        if (tree2 == null) {
            return true;
        }
        if (tree1 == null) {
            return false;
        }
        if (tree1.getValue() != tree2.getValue()) {
            return false;
        }
        return judge(tree1.getLeft(), tree2.getLeft()) && judge(tree1.getRight(), tree2.getRight());
    }
    //建二叉树
    public static BinaryTree build(int[] preList, int[] midList) {
        if (preList == null || preList.length == 0 || midList == null || midList.length == 0 || preList.length != midList.length) {
            return null;
        }
        BinaryTree root = new BinaryTree(preList[0]);
        for (int i = 0; i < preList.length; i++) {
            if (preList[0] == midList[i]) {
                root.setLeft(build(Arrays.copyOfRange(preList, 1, i + 1), Arrays.copyOfRange(midList, 0, i)));
                root.setRight(build(Arrays.copyOfRange(preList, i + 1, preList.length), Arrays.copyOfRange(midList, i + 1, midList.length)));
            }
        }
        return root;
    }
    //先序遍历
    public static void preShow(BinaryTree root) {
        if (root == null) {
            return;
        }
        System.out.printf("%d\t", root.getValue());
        if (root.getLeft() != null) {
            preShow(root.getLeft());
        }
        if (root.getRight() != null) {
            preShow(root.getRight());
        }

    }
}