摘要：
Fang Fang says she wants to be remembered. I promise her. We define the sequence FF of strings. F0 = ‘‘f",F0 = ‘‘f", F1 = ‘‘ff",F1 = ‘‘ff", F2 = ‘‘cff 阅读全文
摘要：
On a grid map there are n little men and n houses. In each unit time, every little man can move one unit step, either horizontally, or vertically, to 阅读全文