#ifndef S0021_MERGE_TWO_SORTED_LISTS
#define S0021_MERGE_TWO_SORTED_LISTS

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) {}
};

#include <limits>

class Solution {
 public:
  ListNode* mergeTwoLists(ListNode* list1, ListNode* list2);
};

#endif