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 Solution {
    
    public boolean HasSubtree(TreeNode root1, TreeNode root2) {
        
        boolean result = false;
        if(root1 != null && root2 != null) {
            
            if(root1.val == root2.val) {
                
                result = judge(root1, root2);
            }
            if(!result) {
                
                result = HasSubtree(root1.left, root2);
            }
            if(!result) {
                
                result = HasSubtree(root1.right, root2);
            }
        }
        return result;
    }
    private boolean judge(TreeNode root1, TreeNode root2) {
        
        if(root2 == null)
            return true;
        if(root1 == null)
            return false;
        if(root1.val != root2.val)
            return false;
        return judge(root1.left, root2.left) && judge(root1.right, root2.right);
    }
}