数的结构

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）

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
import java.util.LinkedList;
public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        if(root2==null||root1==null) return false;
        LinkedList queue = new LinkedList<>();
        queue.add(root1);
        while(queue.size()>0) {
            TreeNode node = queue.pollFirst();
            if(isSubTree(node,root2)) {
                return true;
            }else{
                if(node.left!=null) {
                    queue.add(node.left);
                }
                if(node.right!=null) {
                    queue.add(node.right);
                }
            }
        }
        return false;
    }
    
    public boolean isSubTree(TreeNode root1,TreeNode root2) {
        if(root2==null) return true;
        if(root1==null && root2!=null) return false;
        if(root1.val==root2.val) {
            boolean left = isSubTree(root1.left,root2.left);
            boolean right = isSubTree(root1.right,root2.right);
            return left&right;
        }else{
            return false;
        }
    }
}