In order for other guys to meet him, in #1's point of view, other guys must come towords him. Still in #1's point of view, in order for #3 and #4 to meet #2, #2, #3 and #4 should be on the same line (note that the roads are in general position). Then the problem is simplified to be 1-dimensional. www.ddhw.com
哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
雷达卡
发表于 2005-4-11 23:32:18