LeetCode之Flatten Binary Tree to Linked List

class Solution {public:    void flatten(TreeNode* root) {        if(root == nullptr) return;        flatten(root->left);        flatten(root->right);        if(root->left == nullptr) return;        TreeNode *p(root->left);        while(p->right != nullptr) p = p->right;        p->right = root->right;        root->right = root->left;        root->left = nullptr;    }};