/**public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}*/public class Solution {　　//判断root2是否是root1的子树    public boolean HasSubtree(TreeNode root1,TreeNode root2) {          if(root1 ==null || root2==null) return false;                if(isEqualTree(root1,root2)){            return true;        }else{                   return HasSubtree(root1.left,root2) || HasSubtree(root1.right,root2);        }            }　　//判断B是否是A的子树，并且从根节点开始，即A.val=B.val    public boolean isEqualTree(TreeNode A,TreeNode B){        if(B==null) return true;        if(A==null) return false;        if(A.val != B.val) return false;                return isEqualTree(A.left,B.left) && isEqualTree(A.right,B.right);            } }