2022-10-14 Daily-Challenge

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In: DailyChallenge

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

October LeetCoding Challenge 14

Description

Delete the Middle Node of a Linked List

You are given the head of a linked list. Delete the middle node, and return the head of the modified linked list.

The middle node of a linked list of size n is the ⌊n / 2⌋th node from the start using 0-based indexing, where ⌊x⌋ denotes the largest integer less than or equal to x.

  • For n = 1, 2, 3, 4, and 5, the middle nodes are 0, 1, 1, 2, and 2, respectively.

Example 1:

img

Input: head = [1,3,4,7,1,2,6]
Output: [1,3,4,1,2,6]
Explanation:
The above figure represents the given linked list. The indices of the nodes are written below.
Since n = 7, node 3 with value 7 is the middle node, which is marked in red.
We return the new list after removing this node.

Example 2:

img

Input: head = [1,2,3,4]
Output: [1,2,4]
Explanation:
The above figure represents the given linked list.
For n = 4, node 2 with value 3 is the middle node, which is marked in red.

Example 3:

img

Input: head = [2,1]
Output: [2]
Explanation:
The above figure represents the given linked list.
For n = 2, node 1 with value 1 is the middle node, which is marked in red.
Node 0 with value 2 is the only node remaining after removing node 1.

Constraints:

  • The number of nodes in the list is in the range [1, 10^5].
  • 1 <= Node.val <= 10^5

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  ListNode* deleteMiddle(ListNode* head) {
    ListNode *newHead = new ListNode(0, head);
    ListNode *fast = newHead;
    ListNode *slow = newHead;
    ListNode *cur = newHead;
    while(fast->next && fast->next->next) {
      fast = fast->next;
      if(fast->next) {
        fast = fast->next;
      }
      slow = slow->next;
    }
    slow->next = slow->next->next;
    return newHead->next;
  }
};

// Accepted
// 70 / 70 cases passed (1043 ms)
// Your runtime beats 97.62 % of cpp submissions
// Your memory usage beats 20.46 % of cpp submissions (294.9 MB)
Algorithm