摘要：
Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in 阅读全文
摘要：
You are given a m x n 2D grid initialized with these three possible values. Fill each empty room with the distance to its nearest gate. If it is impos 阅读全文
摘要：
Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacen 阅读全文