摘要：
A group of two or more people wants to meet and minimize the total travel distance. You are given a 2D grid of values 0 or 1, where each 1 marks the h 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：
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