Solution.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* correctBinaryTree(TreeNode* root) {
        unordered_set<TreeNode*> vis;
        function<TreeNode*(TreeNode*)> dfs = [&](TreeNode* root) -> TreeNode* {
            if (!root || vis.count(root->right)) {
                return nullptr;
            }
            vis.insert(root);
            root->right = dfs(root->right);
            root->left = dfs(root->left);
            return root;
        };
        return dfs(root);
    }
};