题解 | 树转链表

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
class Converter {
    ListNode* tail;
    void inorder(TreeNode* root) {
        if(!root) return;
        inorder(root->left);
        auto node = new ListNode(root->val);
        tail->next = node;
        tail = tail->next;
        inorder(root->right);
    }
  public:
    ListNode* treeToList(TreeNode* root) {
        // write code here
        auto dummy_head = new ListNode(0);
        tail = dummy_head;
        inorder(root);

        return dummy_head->next;
    }
};