摘要：You are a hiker preparing for an upcoming hike. You are given heights, a 2D array of size rows x columns, where heights[row][col] represents the heigh 阅读全文

摘要：There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up, down, left or right, but it won't stop roll 阅读全文

摘要：Let's play the minesweeper game (Wikipedia, online game)! You are given a 2D char matrix representing the game board. 'M' represents an unrevealed min 阅读全文

摘要：You want to build a house on an empty land which reaches all buildings in the shortest amount of distance. You can only move up, down, left and right. 阅读全文