#ifndef S0023_MERGE_K_SORTED_LISTS_HPP
#define S0023_MERGE_K_SORTED_LISTS_HPP

#include <vector>

using namespace std;

struct ListNode {
  int val;
  ListNode *next;
  ListNode() : val(0), next(nullptr) {}
  ListNode(int x) : val(x), next(nullptr) {}
  ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class S0023 {
 public:
  ListNode *mergeKLists(vector<ListNode *> &lists);
  ListNode *mergeTwoLists(ListNode *a, ListNode *b);
  ListNode *merge(vector<ListNode *> &lists, int l, int r);
};

#endif