Robina Li

Given an array of positive integers nums and an integer k, return the number of contiguous subarrays where the product of all elements is strictly less than k.

You are given an array prices where prices[i] is the price of a stock on day i. Find the maximum profit with as many transactions as you like, subject to:...

In an infinite chess board with coordinates from -infinity to +infinity, a knight starts at (0, 0). Return the minimum number of moves to reach (x, y).

Implement a SnapshotArray that supports: SnapshotArray(int length) – initializes an array of the given length (all zeros) void set(index, val) – sets the element at index to val int snap()...

Design a hit counter that counts the number of hits received in the past 5 minutes (300 seconds).

Given a binary tree, a node X is good if there is no node with a value greater than X on the path from root to X. Return the number...

A company has n employees numbered 0 to n-1. Each employee has exactly one direct manager given in manager[i], except the head of the company (manager[headID] == -1). An employee...

You are given a 2D array intervals where intervals[i] = [left_i, right_i] represents the inclusive interval [left_i, right_i]. Divide the intervals into one or more groups such that no two...

A gene string is represented by an 8-character string of 'A', 'C', 'G', and 'T'. Given startGene, endGene, and a bank of valid gene strings, return the minimum number of...

There are n rooms labeled 0 to n-1. All rooms are locked except room 0. Each room contains a set of keys to other rooms. Given rooms[i] – the set...