Today I have done leetcode's March LeetCoding Challenge with cpp.

March LeetCoding Challenge 7

Description

Merge Two Sorted Lists

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

Example 1:

Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]

Example 2:

Input: list1 = [], list2 = []
Output: []

Example 3:

Input: list1 = [], list2 = [0]
Output: [0]

Constraints:

• The number of nodes in both lists is in the range [0, 50].
• -100 <= Node.val <= 100
• Both list1 and list2 are sorted in non-decreasing order.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  ListNode* mergeTwoLists(ListNode* a, ListNode* b) {
    ListNode *newHead = new ListNode(0);
    ListNode *cur = newHead;
    while(a && b) {
      if(a->val < b->val) {
        cur->next = a;
        a = a->next;
      } else {
        cur->next = b;
        b = b->next;
      }
      cur = cur->next;
    }
    if(a) cur->next = a;
    else cur->next = b;
    return newHead->next;
  }
};

// Accepted
// 208/208 cases passed (11 ms)
// Your runtime beats 55.46 % of cpp submissions
// Your memory usage beats 15.87 % of cpp submissions (15 MB)