Robina Li

An image smoother is a filter of the size 3 x 3 that can be applied to each cell of an image by rounding down the average of the cell...

You are given a string s and an array of strings words. You should add a closed pair of bold tag <b> and </b> to wrap the substrings in s...

Given a time represented in the format "HH:MM", form the next closest time by reusing the current digits. There is no limit on how many times a digit can be...

You have n bulbs in a row numbered from 1 to n. Initially, all the bulbs are turned off. On day i (for i from 0 to n-1), we turn...

Given two strings a and b, return the minimum number of times you should repeat string a so that string b is a substring of it. If it is impossible...

In this problem, a tree is an undirected graph that is connected and has no cycles.

You are in a city that consists of n intersections numbered from 0 to n - 1 with bi-directional roads between some intersections. The inputs are generated such that you...

There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city...

You are given an array of variable pairs equations and an array of real numbers values, where equations[i] = [Ai, Bi] and values[i] represent the equation Ai / Bi =...

You have a data structure of employee information, including the employee’s unique ID, importance value, and direct subordinates’ IDs.