2022-02-16 Daily-Challenge

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

February 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:

img

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 (3 ms)
// Your runtime beats 70.43 % of cpp submissions
// Your memory usage beats 55.41 % of cpp submissions (7.5 MB)
Algorithm