算法和数据结构 对称的树

对称的树

class Solution {
public:
    bool isSymmetric(TreeNode* root) {
        if(root == NULL) return true;
        return dfs(root->left, root->right);
    }

    bool dfs(TreeNode *lt, TreeNode *rt)
    {
        if(lt == NULL && rt == NULL) return true;
        if(lt == NULL && rt != NULL) return false;
        if(lt != NULL && rt == NULL) return false;
        return (lt->val == rt->val) && dfs(lt->left, rt->right) && dfs(lt->right, rt->left);        
        return true;
    }
};