【力扣hot100题】（045）二叉树展开为链表

快服了我自己了怎么老是把右移节点写成一个l->right没有l=。

/**
 * 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:
    void flatten(TreeNode* root) {
        if(root==nullptr) return ;
        flatten(root->left);
        flatten(root->right);
        if(root->left){
            TreeNode* l=root->left;
            while(l->right) l=l->right;
            l->right=root->right;
            root->right=root->left;
            root->left=nullptr;
        }
    }
};