Robina Li

Given two non-negative integers represented as strings num1 and num2, return their product as a string. You cannot convert the inputs to integers directly (numbers can be very large).

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

The count-and-say sequence is a sequence of digit strings defined by the recursive formula:

You are given an array of k linked lists, each sorted in ascending order. Merge all the linked lists into one sorted linked list and return it.

Two strings are special-equivalent if you can swap characters at even indices among themselves and swap characters at odd indices among themselves, any number of times. Return the number of...

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Given two integers dividend and divisor, divide two integers without using multiplication, division, and mod operator. Return the quotient after dividing dividend by divisor. The integer division should truncate toward...

Problem

Given an integer array nums, return true if you can partition the array into two subsets such that the sum of the elements in both subsets is equal or false...

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.