Problem
You are given the head of a linked list.
Remove every node which has a node with a strictly greater value anywhere to the right side of it.
Return **the *head* of the modified linked list.**
Example 1:
Input: head = [5,2,13,3,8]
Output: [13,8]
Explanation: The nodes that should be removed are 5, 2 and 3.
- Node 13 is to the right of node 5.
- Node 13 is to the right of node 2.
- Node 8 is to the right of node 3.
Example 2:
Input: head = [1,1,1,1]
Output: [1,1,1,1]
Explanation: Every node has value 1, so no nodes are removed.
Constraints:
The number of the nodes in the given list is in the range
[1, 105].1 <= Node.val <= 105
Solution (Java)
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode removeNodes(ListNode head) {
if (head != null) {
head.next = removeNodes(head.next);
if (head.next != null && head.val < head.next.val) {
return head.next;
}
}
return head;
}
}
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).