struct val{
    int v0, v1;
};

class Solution {
public:
    val dfs(TreeNode* node){
        if (node == nullptr)    return {0, 0};

        auto l = dfs(node->left);
        auto r = dfs(node->right);
        int cur0 = max(l.v0, l.v1) + max(r.v0, r.v1);
        int cur1 = node->val + l.v0 + r.v0;
        return {cur0, cur1};
    }

    int rob(TreeNode* root) {
        auto ans = dfs(root);
        return max(ans.v0, ans.v1);

    }
};