【剑指offer】对称的二叉树

先象征性地看一下有没有子树 有的话判断子树是不是镜像的
这种题目先在纸上画画图更直观

class Solution {
public:
    bool isOpposite(TreeNode* left, TreeNode* right){
        if(left == NULL && right == NULL)
            return true;
        if(left == NULL || right == NULL)
            return false;
        if(left->val == right->val)
            return isOpposite(left->left, right->right) && isOpposite(left->right, right->left);
        return false;
    }
    bool isSymmetrical(TreeNode* pRoot)
    {
        if(pRoot == NULL)
            return true;
        return isOpposite(pRoot->left, pRoot->right);
    }

};