Robina Li

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.

You are given a 2D array of axis-aligned rectangles. For each rectangle[i] = [xi1, yi1, xi2, yi2], where (xi1, yi1) is the bottom-left corner and (xi2, yi2) is the top-right...

You are given an m x n grid rooms initialized with these three possible values:

Given an integer n, return the least number of perfect square numbers that sum to n.

Greedy algorithms are among the most elegant tools in competitive programming — when they work, they’re simpler and faster than dynamic programming. This guide covers the core greedy patterns you’ll...

Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window.

You are given an m x n grid where each cell can have one of three values: