1474

1474. Delete N Nodes After M Nodes of a Linked List (Easy)

Given the head of a linked list and two integers m and n. Traverse the linked list and remove some nodes in the following way:

• Start with the head as the current node.
• Keep the first m nodes starting with the current node.
• Remove the next n nodes
• Keep repeating steps 2 and 3 until you reach the end of the list.

Return the head of the modified list after removing the mentioned nodes.

 

Example 1:

Input: head = [1,2,3,4,5,6,7,8,9,10,11,12,13], m = 2, n = 3
Output: [1,2,6,7,11,12]
Explanation: Keep the first (m = 2) nodes starting from the head of the linked List  (1 ->2) show in black nodes.
Delete the next (n = 3) nodes (3 -> 4 -> 5) show in read nodes.
Continue with the same procedure until reaching the tail of the Linked List.
Head of the linked list after removing nodes is returned.

Example 2:

Input: head = [1,2,3,4,5,6,7,8,9,10,11], m = 1, n = 3
Output: [1,5,9]
Explanation: Head of linked list after removing nodes is returned.

Example 3:

Input: head = [1,2,3,4,5,6,7,8,9,10,11], m = 3, n = 1
Output: [1,2,3,5,6,7,9,10,11]

Example 4:

Input: head = [9,3,7,7,9,10,8,2], m = 1, n = 2
Output: [9,7,8]

 

Constraints:

• The number of nodes in the list is in the range [1, 104].
• 1 <= Node.val <= 106
• 1 <= m, n <= 1000

 

Follow up: Could you solve this problem by modifying the list in-place?

Companies:
Microsoft

Related Topics:
Linked List

Similar Questions:

• Remove Nth Node From End of List (Medium)
• Remove Zero Sum Consecutive Nodes from Linked List (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/delete-n-nodes-after-m-nodes-of-a-linked-list/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    ListNode* deleteNodes(ListNode* head, int m, int n) {
        auto p = head;
        while (p) {
            for (int i = 1; i < m && p; ++i) p = p->next;
            if (!p) break;
            auto tail = p;
            p = p->next;
            for (int i = 0; i < n && p; ++i) {
                auto rm = p;
                p = p->next;
                delete rm;
            }
            tail->next = p;
        }
        return head;
    }
};