Robina Li

Design a Tic-Tac-Toe game that is played on an n x n board between two players. A move is guaranteed to be valid and is placed on an empty block....

Given two numbers hour and minutes, return the smaller angle (in degrees) formed between the hour and the minute hand of a clock.

Tic-tac-toe is played on a 3 x 3 grid by two players A and B. Player A always plays first. Given an array moves where moves[i] = [row, col] indicates...

Given a positive integer n, generate an n × n matrix filled with elements from 1 to n² in spiral order (clockwise).

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: