剑指offer（十七）树的子结构

点击进入 牛客网题库：树的子结构

题目描述

输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）

子结构和子树的区别

public class Solution {
  public boolean HasSubtree(TreeNode root1, TreeNode root2) {
        boolean result = false;
        if (root1 != null && root2 != null) {
            //如果这个结果相等
            if (root1.val == root2.val) {
                result = doesTree1HasTree2(root1, root2);
            }
            if (!result) {
                result = HasSubtree(root1.left, root2);
            }
            if (!result) {
                result = HasSubtree(root1.right, root2);
            }
        }

        return result;
    }

    public boolean doesTree1HasTree2(TreeNode node1, TreeNode node2) {
        if (node2 == null) {
            return true;
        }
        if (node1 == null) {
            return false;
        }
        if (node1.val != node2.val) {
            return false;
        }

        return doesTree1HasTree2(node1.left, node2.left)
                && doesTree1HasTree2(node1.right, node2.right);
    }
}