剑指offer算法题：【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）

答案

public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        boolean result = false;
        if(root1!=null&&root2!=null){
            if(root1.val==root2.val){
               result =  doesTree1HaveTree2(root1,root2);
            }
            if(!result){
              result = HasSubtree(root1.left,root2);
            }
            if(!result){
              result = HasSubtree(root1.right,root2);
            }
        }
        return result;
    }
    public static boolean doesTree1HaveTree2(TreeNode node1, TreeNode node2){
        if(node2==null){
            return true;
        }
        if(node1==null){
            return false;
        }
        if(node1.val==node2.val){
            return doesTree1HaveTree2(node1.left,node2.left)&&doesTree1HaveTree2(node1.right,node2.right);
        }
        return false;
    }
}