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

May LeetCoding Challenge 16

Description

Swap Nodes in Pairs

Given a linked list, swap every two adjacent nodes and return its head. You must solve the problem without modifying the values in the list's nodes (i.e., only nodes themselves may be changed.)

Example 1:

Input: head = [1,2,3,4]
Output: [2,1,4,3]

Example 2:

Input: head = []
Output: []

Example 3:

Input: head = [1]
Output: [1]

Constraints:

• The number of nodes in the list is in the range [0, 100].
• 0 <= Node.val <= 100

Solution

class Solution {
public:
  ListNode* swapPairs(ListNode* head) {
    ListNode *newHead = new ListNode(-1, head);
    ListNode *cur = newHead;
    while(head) {
      if(head->next) {
        ListNode *tmp = head->next->next;
        cur->next = head->next;
        head->next->next = head;
        head->next = tmp;
        cur = cur->next->next;
        head = tmp;
      } else {
        head = head->next;
      }
    }
    return newHead->next;
  }
};

// Accepted
// 55/55 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 55.41 % of cpp submissions (7.5 MB)