Given the head of a singly linked list, reverse the list, and return the reversed list.
Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.
Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice.