再次递归：） | #对称的二叉树#

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    bool isSym(TreeNode* left, TreeNode* right) {
        if (!left && !right) return true;
        else if (!left || !right || left->val!=right->val) return false;
        else return isSym(left->left, right->right) && isSym(left->right, right->left);
    }
    bool isSymmetrical(TreeNode* pRoot) {
        if (!pRoot) return true;
        else return isSym(pRoot->left, pRoot->right);
    }

};