Given a string s, return the longest palindromic substring in s.
Given a non-empty array of integers, return the k most frequent elements.
Imagine you are writing a small compiler for your college project and one of the tasks (or say sub-tasks) for the compiler would be to detect if the parenthesis are in place or not.
On a broken calculator that has a number showing on its display, we can perform two operations
Given the root node of a binary search tree, return the sum of values of all nodes with a value between L and R (inclusive). The binary search tree is guaranteed to have unique values.
Given a list of pairs of equivalent words synonyms and a sentence text, Return all possible synonymous sentences sorted lexicographically.
Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.
Given two words (beginWord and endWord), and a dictionary of word list, find the length of the shortest transformation sequence from beginWord to endWord
Roman numerals are usually written from largest to smallest, and from left to right. However, the numeral for four is not IIII; instead, it is written as IV.
Given a set of points in the xy-plane, determine the minimum area of a rectangle formed from these points, with sides parallel to the x and y axes. If there isn’t any rectangle, return 0.