摘要：
Given a 2D grid, each cell is either a wall 2, an house 1or empty 0 (the number zero, one, two), find a place to build a post office so that the sum o 阅读全文
摘要：
Design an algorithm and write code to serialize and deserialize a binary tree. Writing the tree to a file is called 'serialization' and reading back f 阅读全文