2487. Remove Nodes From Linked List

ramnayan — Sat, 30 May 2026 18:22:34 +0000

In this post i'm gone explain liked list an famous leetcode problem that is "Remove Nodes from linked list".

Problem Statement:
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.

Explanation:
In this problem statement state that remove the nodes which have the right side (any place) element greater than. let's understand with given example.

Node 13 is the right side of the 5,2 nodes thats why 2,5 should be remove.
Node 8 is the right side of 3 node thats why 3 should be remove.

final result would be [13,8]

Solution of the problem:

`/**
 * 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}
 */

const reverList = function(head){
    let prev = null;
    let curr = head;
    let next = null;

    while(curr!=null){
        next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }

    return prev;
}

var removeNodes = function(head) {
    // reverse list
    let reversList = reverList(head);

    let maxNode =  reversList;
    let prevNode = reversList;
    let currNode = reversList.next;
    // removed list
    while(currNode != null){
        if(maxNode.val > currNode.val){
            currNode = currNode.next;
        }else{
            maxNode = currNode;
            prevNode.next = currNode;
            prevNode = prevNode.next;
            currNode = currNode.next;
        }
    }

    prevNode.next = null;
    // reverse list
    return reverList(reversList);
};`

If you have any query or suggestions leave your expression👨🏿‍💻🙌.

Longest Repeating Character Replacement Explanation

ramnayan — Sun, 26 Oct 2025 01:54:51 +0000

I'm writing this post about an specific data structure and algorithm well known problem that is "Longest Repeating Character Replacement".

I have tried to solve this problem with javascript and using two popular algorithm that is Two-Pointer & Sliding-Window.

I hope you are aware of these two algorithms. if you don't know don't worry bellow i have mention the blogs link you can explore or you can find on the google.

Two Pointer - https://www.geeksforgeeks.org/dsa/two-pointers-technique/

Sliding Window - https://www.geeksforgeeks.org/dsa/window-sliding-technique/

Problem start here********

You are given a string s and an integer k. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most k times.

Example 1:

Input: s = "ABAB", k = 2
Output: 4
Explanation: Replace the two 'A's with two 'B's or vice versa.
Example 2:

Input: s = "AABABBA", k = 1
Output: 4
Explanation: Replace the one 'A' in the middle with 'B' and form "AABBBBA".
The substring "BBBB" has the longest repeating letters, which is 4.
There may exists other ways to achieve this answer too.

Explanation*************

Initialise the required variables left right maxLength maxChar and count.

first loop start from string zero index that is right & right. left start when K become zero or (r-l+1)-maxChar>K condition true it means window shrinking.

count variable stores the character frequency to find the maxChar.

var characterReplacement = function(s, k) {
        if(s.length==1) return 1;
        let l=r=maxChar=maxLength=0;
        let count={};

        for(let r=0; r<s.length;r++){
             if(s[r] in count){
                ....
            }else ....;
            maxChar = Math.max(maxChar, count[s[r]]);
            while((r-l+1)-maxChar>k){
                .....
            }
            maxLength=Math.max(maxLength, (r-l+1));
        }
        return maxLength;
};

This is the my best approach that i have used if you have any suggestions please put your thought.

Thanks for stay to the end👍🙈

DEV Community: ramnayan

2487. Remove Nodes From Linked List

Longest Repeating Character Replacement Explanation

Problem start here********

Explanation*************