2022-09-28 Daily-Challenge

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

September LeetCoding Challenge 28

Description

Remove Nth Node From End of List

Given the head of a linked list, remove the nth node from the end of the list and return its head.

Example 1:

img

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Example 2:

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

Example 3:

Input: head = [1,2], n = 1
Output: [1]

Constraints:

  • The number of nodes in the list is sz.
  • 1 <= sz <= 30
  • 0 <= Node.val <= 100
  • 1 <= n <= sz

Follow up: Could you do this in one pass?

Solution

class Solution {
public:
  ListNode* removeNthFromEnd(ListNode* head, int n) {
    ListNode *newHead = new ListNode(-1, head);
    ListNode *tail = newHead;
    ListNode *del = newHead;
    while(n--) tail = tail->next;
    while(tail->next) {
      tail = tail->next;
      del = del->next;
    }
    del->next = del->next->next;
    return newHead->next;
  }
};

// Accepted
// 208/208 cases passed (11 ms)
// Your runtime beats 27.59 % of cpp submissions
// Your memory usage beats 32.26 % of cpp submissions (10.8 MB)
Algorithm