965. 单值二叉树

原题链接：965. 单值二叉树

Solution:

class Solution {
public:
    bool isUnivalTree(TreeNode* root) {
        if(root == nullptr) return true;
        if(root->left != nullptr && root->left->val != root->val) return false;
        if(root->right != nullptr && root->right->val != root->val) return false;
        return isUnivalTree(root->left) && isUnivalTree(root->right);
    }
};