Problem
You are given the head of a linked list.
Remove every node which has a node with a 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
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var removeNodes = function(head) {
var newHead = new ListNode(Number.MAX_SAFE_INTEGER, head);
var stack = [newHead];
var current = head;
while (current) {
while (current.val > stack[stack.length - 1].val) {
stack.pop();
}
stack[stack.length - 1].next = current;
stack.push(current);
current = current.next;
}
return newHead.next;
};
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).