January 2025

Given an mxn matrix, return all elements of the matrix in spiral order.

Given an mxn integer matrix matrix, if an element is 0, set its entire row and column to 0's.

You must do it in place.

You are given the head of a singly linked-list. The list can be represented as:

L0 → L1 → … → Ln – 1 → Ln
Reorder the list to be on the following form:

L0 → Ln → L1 → Ln – 1 → L2 → Ln – 2 → …
You may not modify the values in the list's nodes. Only nodes themselves may be changed.

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

Given an array of meeting time intervals where intervals[i] = [starti, endi], determine if a person could attend all meetings.

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

ou are given an integer n. There are n rooms numbered from 0 to n – 1.

You are given a 2D integer array meetings where meetings[i] = [starti, endi] means that a meeting will be held during the half-closed time interval [starti, endi). All the values of starti are unique.

Meetings are allocated to rooms in the following manner:

Each meeting will take place in the unused room with the lowest number.
If there are no available rooms, the meeting will be delayed until a room becomes free. The delayed meeting should have the same duration as the original meeting.
When a room becomes unused, meetings that have an earlier original start time should be given the room.
Return the number of the room that held the most meetings. If there are multiple rooms, return the room with the lowest number.

A half-closed interval [a, b) is the interval between a and b including a and not including b.

Given an array of meeting time intervals intervals where intervals[i] = [starti, endi], return the minimum number of conference rooms required.

You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.

Merge all the linked-lists into one sorted linked-list and return it.