摘要：
Alice and Bob are playing a game with nn piles of stones. It is guaranteed that nn is an even number. The ii-th pile has aiai stones. Alice and Bob wi 阅读全文
摘要：
SaMer is building a simple robot that can move in the four directions: up (^), down (v), left (<), and right (>). The robot receives the commands to m 阅读全文